Photoacid generators, chemically amplified resist compositions, and patterning process

ABSTRACT

A photoacid generator has formula (1) wherein R is H, F, Cl, nitro, alkyl or alkoxy, n is 0 or 1, m is 1 or 2, r is an integer of 0-4, and r′ is an integer of 0-5. A chemically amplified resist composition comprising the photoacid generator has advantages including a high resolution, focus latitude, long-term PED dimensional stability, and a satisfactory pattern profile shape. When the photoacid generator is combined with a resin having acid labile groups other than those of the acetal type, resolution and top loss are improved. The composition is suited for deep UV lithography.

CROSS-REFERENCE TO RELATED APPLICATION

This non-provisional application claims priority under 35 U.S.C. §119(a)on Patent Application No. 2006-160575 filed in Japan on Jun. 9, 2006,the entire contents of which are hereby incorporated by reference.

TECHNICAL FIELD

This invention relates to photoacid generators for chemically amplifiedresist compositions, chemically amplified resist compositions comprisingthe photoacid generators, and a patterning process using the same. Thechemically amplified resist compositions are sensitive to such radiationas UV, deep UV, electron beams, x-rays, excimer laser beams, γ-rays, andsynchrotron radiation and suitable for the microfabrication ofintegrated circuits.

BACKGROUND OF THE INVENTION

While a number of efforts are currently being made to achieve a finerpattern rule in the drive for higher integration and operating speeds inLSI devices, deep-ultraviolet lithography is thought to hold particularpromise as the next generation in microfabrication technology.

One technology that has attracted a good deal of attention recentlyutilizes as the deep UV light source a high-intensity KrF excimer laserand an ArF excimer laser of a shorter wavelength. There is a desire tohave a microfabrication technique of finer definition by combiningexposure light of shorter wavelength with a resist material having ahigher resolution.

In this regard, the recently developed, acid-catalyzed, chemicalamplification type resist materials are expected to comply with the deepUV lithography because of their many advantages including highsensitivity, resolution and dry etching resistance. The chemicallyamplified resist materials include positive working materials that leavethe unexposed areas with the exposed areas removed and negative workingmaterials that leave the exposed areas with the unexposed areas removed.

In a chemically amplified positive resist composition to be developedwith an alkaline developer, a resin and/or compound in which analkali-soluble phenol or carboxylic acid is partially or entirelyprotected with acid labile protective groups (commonly referred to as“acid labile groups”) is catalytically decomposed with the acidgenerated upon exposure, to generate the phenol or carboxylic acid inexposed areas, whereupon the exposed areas are removed with the alkalinedeveloper. In a similar negative resist composition, a resin and/orcompound having an alkali-soluble phenol or carboxylic acid and acompound capable of bonding or crosslinking said resin or compound underthe action of an acid (referred to as “acid crosslinker”) arecrosslinked with the acid generated upon exposure, to render exposedareas insoluble in an alkaline developer, whereupon unexposed areas areremoved with the alkaline developer.

On use of the chemically amplified positive resist composition, a resistfilm is formed by dissolving a resin having acid labile groups as abinder and a compound capable of generating an acid upon exposure toradiation (referred to as “photoacid generator”) in a solvent, applyingthe resist solution onto a substrate by a variety of methods, andevaporating off the solvent optionally by heating. The resist film isthen exposed to radiation, for example, deep UV through a mask of apredetermined pattern. This is optionally followed by post-exposurebaking (PEB) for promoting acid-catalyzed reaction. The exposed resistfilm is developed with an aqueous alkaline developer for removing theexposed areas of the resist film, obtaining a positive pattern profile.The substrate is then etched by any desired technique. Finally theremaining resist film is removed by dissolution in a remover solution orashing, leaving the substrate having the desired pattern profile.

The chemically amplified positive resist composition adapted for KrFexcimer lasers generally uses a phenolic resin, for example,polyhydroxystyrene in which some or all of the hydrogen atoms ofphenolic hydroxyl groups are protected with acid labile protectivegroups. Iodonium salts, sulfonium salts, bissulfonyldiazomethanecompounds, N-sulfonyloxydicarboxyimide compounds andO-arenesulfonyloxime compounds are typically used as the photoacidgenerator. If necessary, there are added additives, for example, adissolution inhibiting or promoting compound in the form of a carboxylicacid and/or phenol derivative having a molecular weight of up to 3,000in which some or all of the hydrogen atoms of carboxylic acid and/orphenolic hydroxyl groups are protected with acid labile groups, acarboxylic acid compound for improving dissolution characteristics, abasic compound for improving contrast, and a surfactant for improvingcoating characteristics.

The photoacid generators in the form of O-arenesulfonyloxime compoundsas shown below have a satisfactory sensitivity and resolution and arefree of such drawbacks as poor compatibility with resins and lowsolubility in resist solvents as found with other photoacid generatorslike sulfonium salts and iodonium salts. They are advantageously used asthe photoacid generators in chemically amplified resist compositions,especially chemically amplified positive resist compositions adapted forKrF excimer laser. See U.S. Pat. No. 6,004,724 and JP-A 2004-4614.

As the requisite pattern size is reduced, however, even the use ofresist compositions having these photoacid generators combined with theexisting acid labile group-bearing resins encounters problems includinga poor resolution and a failure to form a satisfactory pattern profileon highly reflective substrate.

For resolution improvement, it is a practice to use more acid labilegroups, typically more acid labile acetal groups. However, the reductionof pattern size invites a tendency of reducing the thickness of resistfilm as well. When a phenolic resin having acid labile groups of acetaltype is used, the resist surface becomes more dissolvable. Thedissolution of the resist pattern at the top raises problems including atop loss that the pattern profile shape is rounded at the top, or in thecase of a contact hole pattern, a failure to form a satisfactory patternshape due to a lowering of side robe margin (dissolution by a traceamount of leakage or interference light to unexposed areas). When theresist is applied onto inorganic substrates such as SiON substrateswhich are highly reflective substrates, there arises a problem thatstanding waves prevent formation of a satisfactory pattern shape. Oneapproach for avoiding these problems is to use resins having acid labilegroups of tertiary ether or tertiary ester type which are less labilethan the acid labile groups of acetal type. This approach is successfulin reducing the top loss, but still fails to form a rectangularmicro-pattern and is low in resolution.

For micropatterning purposes, it is also a practice to add the step ofchanging the shape of a resist pattern after its formation throughexposure and development. Exemplary methods include a “thermal flow”method of heating the resist pattern at a temperature equal to or higherthan the glass transition temperature to fluidize the resist film forthereby reducing the hole size, and a “chemical shrink” method offorming a pattern profile, applying thereto a material capable ofreacting with the resist surface (chemically shrinkable material),heating or whole exposure to bond the shrinkable material to the resistpattern sidewall for thereby reducing the space size.

When it is desired to apply the thermal flow method, some acidgenerators can be pyrolyzed during heating, making it difficult tocontrol the flow. This propensity manifests, for example, when aphotoacid generator having a relatively low pyrolysis temperature iscontained in a noticeable amount.

Under these circumstances, U.S. Pat. No. 6,004,724 describes anO-oximesulfonate compound which generates tosyloxybenzene-sulfonic acidupon light exposure. The use of these compounds is still unsatisfactoryin forming a resist pattern with a reduced feature size from a thinresist film.

The photoacid generator for use in resist compositions is required tohave a fully high solubility (or compatibility) in resist solvents andresins, good storage stability, non-toxicity, ease of application,pattern profile shape, PED stability, high resolution, wide focal depth,and high sensitivity. Prior art photoacid generators, especiallyO-arenesulfonyloxime compound photoacid generators do not satisfy allthese requirements.

In the recent stage when the pattern feature of integrated circuitsbecomes more miniaturized, more stringent requirements are imposed onthe problem of high resolution accompanied with a resist thicknessreduction.

DISCLOSURE OF THE INVENTION

An object of the invention is to provide a photoacid generator used toformulate a chemically amplified resist composition which is improved inthe control of pattern profile shape, thermal flow and other parametersparticularly when the thickness of resist film is reduced; a resistcomposition comprising the same; and a patterning process.

We have found that a chemically amplified resist composition comprisingan O-arenesulfonyloxime compound of the general formula (1), especiallyformula (1a), shown below, possesses a number of great advantagesincluding dissolution, storage stability, effective coating, minimizedline width variation or shape degradation during long-term PED, goodpattern profile shape particularly at reduced film thickness, and a highresolution enough for microfabrication, particularly when processed bydeep UV lithography.

The present invention provides a photoacid generator, a chemicallyamplified resist composition comprising the same, and a patterningprocess, as defined below.

-   [1] A photoacid generator for use in chemically amplified resist    compositions, having the general formula (1):

wherein R is independently selected from the class consisting ofhydrogen, fluorine, chlorine atoms, nitro groups, and substituted orunsubstituted, straight, branched or cyclic alkyl and alkoxy groups of 1to 12 carbon atoms, n is 0 or 1, m is 1 or 2, r is an integer of 0 to 4,and r′ is an integer of 0 to 5.

-   [2] A photoacid generator for use in chemically amplified resist    compositions, having the formula (1a).

-   [3] A chemically amplified resist composition comprising

(A) a resin which changes its solubility in an alkaline developer underthe action of an acid, and

(B) the photoacid generator of [1] or [2].

-   [4] A chemically amplified positive resist composition comprising

(A) a resin which changes its solubility in an alkaline developer underthe action of an acid, and

(B) the photoacid generator of [1] or [2].

-   [5] The resist composition of [3] or [4], further comprising (C) a    compound capable of generating an acid upon exposure to radiation,    other than component (B).-   [6] The resist composition of [3] or [4] wherein the resin (A) has    such substituent groups having C—O—C linkages that the solubility in    an alkaline developer changes as a result of scission of the C—O—C    linkages under the action of an acid.-   [7] The resist composition of [6] wherein the resin (A) is a polymer    containing phenolic hydroxyl groups in which hydrogen atoms of the    phenolic hydroxyl groups are substituted with acid labile groups of    one or more types in a proportion of more than 0 mol % to 80 mol %    on the average of the entire hydrogen atoms of the phenolic hydroxyl    groups, the polymer having a weight average molecular weight of    3,000 to 100,000.-   [8] The resist composition of [6] wherein the resin (A) is a polymer    comprising recurring units of the following general formula (2a):

wherein R¹ is hydrogen or methyl, R² is a straight, branched or cyclicalkyl group of 1 to 8 carbon atoms, x is 0 or a positive integer, y is apositive integer, satisfying x+y≦5, R³ is an acid labile group, S and Tare positive integers, satisfying 0<T/(S+T)≦0.8,

wherein the polymer contains units in which hydrogen atoms of phenolichydroxyl groups are partially substituted with acid labile groups of oneor more types, a proportion of the acid labile group-bearing units is onthe average from more than 0 mol % to 80 mol % based on the entirepolymer, and the polymer has a weight average molecular weight of 3,000to 100,000.

-   [9] The resist composition of [6] wherein the resin (A) is a polymer    comprising recurring units of the following general formula (2a′):

wherein R¹ is hydrogen or methyl, R² is a straight, branched or cyclicalkyl group of 1 to 8 carbon atoms, R³ is an acid labile group, R^(3a)is hydrogen or an acid labile group, at least some of R^(3a) being acidlabile groups, x is 0 or a positive integer, y is a positive integer,satisfying x+y≦5, M and N are positive integers, L is 0 or a positiveinteger, satisfying 0<N/(M+N+L)≦0.5 and 0<(N+L)/(M+N+L)≦0.8,

wherein the polymer contains on the average from more than 0 mol % to 50mol % of those units derived from acrylate and methacrylate, and alsocontains on the average from more than 0 mol % to 80 mol % of acidlabile group-bearing units, based on the entire polymer, and the polymerhas a weight average molecular weight of 3,000 to 100,000.

-   [10] The resist composition of [6] wherein the resin (A) is a    polymer comprising recurring units of the following general formula    (2a″):

wherein R¹ is hydrogen or methyl, R² is a straight, branched or cyclicalkyl group of 1 to 8 carbon atoms, R³ is an acid labile group, R^(3a)is hydrogen or an acid labile group, at least some of R^(3a) being acidlabile groups, x is 0 or a positive integer, y is a positive integer,satisfying x+y≦5, yy is 0 or a positive integer, satisfying x+yy≦4, Aand B are positive integers, C, D and E each are 0 or a positiveinteger, satisfying 0<(B+E)/(A+B+C+D+E)≦0.5 and0<(C+D+E)/(A+B+C+D+E)≦0.8,

wherein the polymer contains on the average from more than 0 mol % to 50mol % of those units derived from indene and/or substituted indene, andalso contains on the average from more than 0 mol % to 80 mol % of acidlabile group-bearing units, based on the entire polymer, and the polymerhas a weight average molecular weight of 3,000 to 100,000.

-   [11] The resist composition of any one of [6] to [10] wherein the    acid labile group is a tertiary alkyl group of 4 to 20 carbon atoms    or a group of the following general formula (5):

wherein R⁸ is a straight, branched or cyclic alkyl group of 1 to 8carbon atoms or an aryl group of 6 to 20 carbon atoms which may besubstituted, h is 0 or 1, i is 0, 1, 2 or 3, satisfying 2h+i=2 or 3.

-   [12] The resist composition of any one of [3] to [11], further    comprising (D) a basic compound.-   [13] The resist composition of any one of [3] to [12], further    comprising (E) an organic acid derivative.-   [14] The resist composition of any one of [3] to [13], further    comprising (F) an organic solvent which is a propylene glycol alkyl    ether acetate, an alkyl lactate or a mixture thereof.-   [15] A process for forming a pattern, comprising the steps of:

(i) applying the resist composition of any one of [3] to [14] onto asubstrate to form a coating,

(ii) heat treating the coating and exposing the coating to high energyradiation with a wavelength of up to 300 nm or electron beam through aphotomask,

(iii) optionally heat treating the exposed coating, and developing thecoating with a developer.

-   [16] A process for forming a pattern, comprising the steps of:

(i) applying the resist composition of any one of [3] to [14] onto aninorganic substrate such as a SiON film to form a coating,

(ii) heat treating the coating and exposing the coating to high energyradiation with a wavelength of up to 300 nm or electron beam through aphotomask,

(iii) optionally heat treating the exposed coating, and developing thecoating with a developer.

-   [17] A process for forming a pattern, comprising the steps of:

(i) applying the resist composition of any one of [3] to [14] onto asubstrate to form a coating,

(ii) heat treating the coating and exposing the coating to high energyradiation with a wavelength of up to 300 nm or electron beam through aphotomask,

(iii) optionally heat treating the exposed coating, and developing thecoating with a developer to form a pattern profile, and

(iv) heat treating for causing the pattern profile to flow for therebyreducing its size.

BENEFITS OF THE INVENTION

The chemically amplified resist composition comprising a photoacidgenerator capable of generating an acid upon exposure to actinicradiation according to the invention has many advantages includingdissolution, focus latitude, minimized line width variation or shapedegradation even on long-term PED, a satisfactory pattern profile shapeafter development, and a high resolution enough for microfabrication.Particularly when the photoacid generator is combined with a resinhaving acid labile groups other than those of the acetal type, a highresolution is achieved and the resist shape is improved because thedissolution of resist film top portion in unexposed areas is restrained.The composition is thus suited for microfabrication, especially by deepUV lithography.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Photoacid Generator

In the first embodiment, the invention provides a photoacid generatorhaving an arenesulfonyloxyarenesulfonyl group for use in chemicallyamplified resist compositions, represented by the general formula (1) orformula (1a).

Herein R is independently selected from among a hydrogen atom, fluorineatom, chlorine atom, nitro group, and a substituted or unsubstituted,straight, branched or cyclic alkyl or alkoxy group of 1 to 12 carbonatoms. The subscript N is 0 or 1, m is 1 or 2, r is an integer of 0 to4, and r′ is an integer of 0 to 5.

In formula (1), R which may be the same or different stands for ahydrogen atom, a fluorine atom, a chlorine atom, a nitro group, or asubstituted or unsubstituted, straight, branched or cyclic alkyl oralkoxy group of 1 to 12 carbon atoms, for example, hydrogen, methyl,ethyl, n-propyl, sec-propyl, cyclopropyl, n-butyl, sec-butyl, iso-butyl,tert-butyl, methoxy, ethoxy, n-propyloxy, sec-propyloxy, n-butyloxy,sec-butyloxy, iso-butyloxy, tert-butyloxy, n-hexyl, n-hexyloxy, n-octyl,n-octyloxy, n-decyl, n-decyloxy, n-dodecyl, and n-dodecyloxy groups. Ofthese, hydrogen, methyl, ethyl, n-hexyloxy, and n-octyloxy groups arepreferred, with hydrogen and methyl being more preferred. The subscriptn is 0 or 1, m is 1 or 2, r is an integer of 0 to 4, and r′ is aninteger of 0 to 5. An arylsulfonyloxy group may substitute on anarenesulfonyl group at any desired position, that is, the substitutionposition is not particularly limited. In a preferred example, when thearenesulfonyl group is benzenesulfonyl, the preferred substitutionposition is 4-position; when the arenesulfonyl group isnaphthalenesulfonyl, the preferred substitution position differs whetherthe group is 1- or 2-naphthalenesulfonyl; the preferred substitutionposition is 4-, 5- or 8-position when the group is1-naphthalenesulfonyl, and 6-position when the group is2-naphthalenesulfonyl.

Illustrative examples of (arylsulfonyloxy)arenesulfonyloxy groupinclude, but are not limited to,4-(4′-toluenesulfonyloxy)benzenesulfonyloxy,4-(benzenesulfonyloxy)benzenesulfonyloxy,4-(4′-methoxybenzenesulfonyloxy)benzenesulfonyloxy,4-(4′-fluorobenzenesulfonyloxy)benzenesulfonyloxy,4-(4′-trifluoromethylbenzenesulfonyloxy)benzenesulfonyloxy,4-(pentafluorobenzenesulfonyloxy)benzenesulfonyloxy,4-(2-naphthalenesulfonyloxy)benzenesulfonyloxy,3-methoxy-4-(4′-toluenesulfonyloxy)benzenesulfonyloxy,3-methyl-4-(4′-toluenesulfonyloxy)benzenesulfonyloxy,2-(4′-toluenesulfonyloxy)naphthalene-6-sulfonyloxy,1-(4′-toluenesulfonyloxy)naphthalene-4-sulfonyloxy,1-(4′-toluenesulfonyloxy)naphthalene-8-sulfonyloxy,2,5-bis(4′-toluenesulfonyloxy)benzenesulfonyloxy, and2,5-bis(4′-methoxybenzenesulfonyloxy)benzenesulfonyloxy.

The O-arenesulfonyloxime compound of formula (1) or (1a) has an oximeskeleton which can be synthesized by reacting a substitutedphenylacetonitrile compound with 2-nitrothiophene in an alcohol solventunder basic conditions. The sulfonic acid moiety can be synthesized bythe following method although the synthesis method is not limitedthereto.

The (arylsulfonyloxy)arenesulfonic acid can be synthesized according tothe teaching of JP-A 2001-122850. Specifically sodium(arylsulfonyloxy)arenesulfonate or the like is obtainable by reacting ahydroxyarenesulfonic acid or hydroxyarenesulfonic acid salt with anarenesulfonyl halide or arenesulfonic acid anhydride in the presence ofa base such as sodium hydroxide or potassium hydroxide.

Suitable examples of the hydroxyarenesulfonic acid include, but are notlimited to, 4-phenolsulfonic acid, 3-methyl-4-phenolsulfonic acid,3-methoxy-4-phenolsulfonic acid, 3-nitro-4-phenolsulfonic acid,hydroquinone-2-sulfonic acid, 1,4-naphtholsulfonic acid,1,5-naphtholsulfonic acid, 2,6-naphtholsulfonic acid,1,8-naphtholsulfonic acid, 6,7-dihydroxy-2-naphthalenesulfonic acid, and5,7-dinitro-8-hydroxy-2-naphthalenesulfonic acid. Suitable examples ofthe arylsulfonyl halide include, but are not limited to, benzenesulfonylchloride, 4-toluenesulfonyl chloride, 4-ethylbenzenesulfonyl chloride,4-methoxybenzenesulfonyl chloride, 4-fluorobenzenesulfonyl chloride,4-trifluoromethylbenzenesulfonyl chloride,2,4,6-trimethylbenzenesulfonyl chloride, pentafluorobenzenesulfonylchloride, and 2-naphthalenesulfonyl chloride.

Further the resulting sulfonic acid or sulfonic acid salt is convertedinto a sulfonyl halide using phosphorus pentachloride or thionylchloride. For the synthesis of sulfonyl chloride from sulfonic acidsalt, reference should be made to the synthesis method described in theabove-cited JP-A 2004-4614.

The target O-sulfonyloxime compound is preferably prepared by dissolvingan oxime compound and a corresponding sulfonyl halide or sulfonic acidanhydride in a solvent such as THF or CH₂Cl₂, and effecting reactionunder basic conditions. Also preferably, the reaction may be effected ina basic solvent such as pyridine.

The substituent group on the O-arenesulfonyloxime compound havingformula (1) is as defined above. Preferred examples of the arenesulfonylmoiety are shown below, but not limited thereto.

Resist Composition

In the second embodiment, the present invention provides a chemicallyamplified resist composition comprising a photoacid generator of theformula (1) or (1a), the composition being sensitive to such radiationas ultraviolet radiation, deep ultraviolet radiation, electron beams,x-rays, excimer laser beams, gamma-rays or synchrotron radiation andsuitable for the microfabrication of integrated circuits. The resistcomposition may be either positive or negative. From the standpoint ofresolution and the like, positive resist compositions are morepreferred.

The resist compositions of the invention include a variety ofembodiments:

1) a chemically amplified positive working resist composition comprising(A) a resin which changes its solubility in an alkaline developer underthe action of an acid, (B) the photoacid generator of formula (1) or(1a), and (F) an organic solvent;

2) a chemically amplified positive resist composition of 1) furthercomprising (C) a photoacid generator capable of generating an acid uponexposure to radiation other than component (B);

3) a chemically amplified positive resist composition of 1) or 2)further comprising (D) a basic compound;

4) a chemically amplified positive resist composition of 1) to 3)further comprising (E) an organic acid derivative; and

5) a chemically amplified positive resist composition of 1) to 4)further comprising (G) a compound with a molecular weight of up to 3,000which changes its solubility in an alkaline developer under the actionof an acid; as well as

6) a chemically amplified negative working resist composition comprising(B) the photoacid generator of formula (1) or (1a), (F) an organicsolvent, (H) an alkali-soluble resin, and (I) an acid crosslinker whichforms a crosslinked structure under the action of an acid;

7) a chemically amplified negative resist composition of 6) furthercomprising the above component (C);

8) a chemically amplified negative resist composition of 6) or 7)further comprising the above component (D); and

9) a chemically amplified negative resist composition of 6) to 8)further comprising (J) an alkali-soluble compound having a molecularweight of up to 2,500; but not limited thereto.

Now the respective components are described in detail.

Component (A)

Component (A) is a resin which changes its solubility in an alkalinedeveloper solution under the action of an acid. In the case ofchemically amplified positive resist compositions, it is preferably,though not limited thereto, an alkali-soluble resin having phenolichydroxyl and/or carboxyl groups in which some or all of the phenolichydroxyl and/or carboxyl groups are protected with acid-labileprotective groups having a C—O—C linkage.

The alkali-soluble resins having phenolic hydroxyl and/or carboxylgroups include homopolymers and copolymers of p-hydroxystyrene,m-hydroxystyrene, α-methyl-p-hydroxystyrene, 4-hydroxy-2-methylstyrene,4-hydroxy-3-methylstyrene, hydroxyindene, methacrylic acid and acrylicacid, and such copolymers having a carboxylic derivative or diphenylethylene introduced at their terminus.

Also included are copolymers in which other units are introduced inaddition to the above-described units in such a proportion that thesolubility in an alkaline developer may not be extremely reduced.Suitable other units are units free of alkali-soluble sites such asunits derived from styrene, α-methylstyrene, acrylate, methacrylate,hydrogenated hydroxystyrene, maleic anhydride, maleimide, andsubstituted or unsubstituted indene. Substituents on the acrylates andmethacrylates may be any of the substituents which do not undergoacidolysis. Exemplary substituents are straight, branched or cyclic C₁₋₈alkyl groups and aromatic groups such as aryl groups, but not limitedthereto.

Examples of the alkali-soluble resins or polymers are given below. Theymay be used as the raw material for the resin (A) which changes itssolubility in an alkaline developer solution under the action of an acidor as the alkali-soluble resin (H). Examples includepoly(p-hydroxystyrene), poly(m-hydroxystyrene),poly(4-hydroxy-2-methylstyrene), poly(4-hydroxy-3-methylstyrene),poly(α-methyl-p-hydroxystyrene), partially hydrogenated p-hydroxystyrenecopolymers, p-hydroxystyrene-α-methyl-p-hydroxystyrene copolymers,p-hydroxystyrene-α-methylstyrene copolymers, p-hydroxystyrene-styrenecopolymers, p-hydroxystyrene-m-hydroxystyrene copolymers,p-hydroxystyrene-styrene copolymers, p-hydroxystyrene-indene copolymers,p-hydroxystyrene-acrylic acid copolymers, p-hydroxystyrene-methacrylicacid copolymers, p-hydroxystyrene-methyl acrylate copolymers,p-hydroxystyrene-acrylic acid-methyl methacrylate copolymers,p-hydroxystyrene-methyl methacrylate copolymers,p-hydroxystyrene-methacrylic acid-methyl methacrylate copolymers,poly(methacrylic acid), poly(acrylic acid), acrylic acid-methyl acrylatecopolymers, methacrylic acid-methyl methacrylate copolymers, acrylicacid-maleimide copolymers, methacrylic acid-maleimide copolymers,p-hydroxystyrene-acrylic acid-maleimide copolymers, andp-hydroxystyrene-methacrylic acid-maleimide copolymers, but are notlimited to these combinations.

Preferred are poly(p-hydroxystyrene), partially hydrogenatedp-hydroxystyrene copolymers, p-hydroxystyrene-styrene copolymers,p-hydroxystyrene-indene copolymers, p-hydroxystyrene-acrylic acidcopolymers, and p-hydroxystyrene-methacrylic acid copolymers.

Alkali-soluble resins comprising recurring units of the followingformula (2), (2′) or (2″) are especially preferred.

Herein R¹ is hydrogen or methyl, R² is a straight, branched or cyclicalkyl group of 1 to 8 carbon atoms, x is 0 or a positive integer, y is apositive integer, satisfying x+y≦5, M and N are positive integers,satisfying 0<N/(M+N)≦0.5, yy is 0 or a positive integer, satisfyingx+yy≦4, and A and B are positive integers, and C is 0 or a positiveinteger, satisfying 0<B/(A+B+C)≦0.5.

The polymer of formula (2″) can be synthesized, for example, byeffecting thermal polymerization of an acetoxystyrene monomer, atertiary alkyl (meth)acrylate monomer and an indene monomer in anorganic solvent in the presence of a radical initiator, and subjectingthe resulting polymer to alkaline hydrolysis in an organic solvent fordeprotecting the acetoxy group, for thereby forming a ternary copolymerof hydroxystyrene, tertiary alkyl (meth)acrylate and indene. The organicsolvent used during polymerization is exemplified by toluene, benzene,tetrahydrofuran, diethyl ether and dioxane. Exemplary polymerizationinitiators include 2,2′-azobisisobutyronitrile,2,2′-azobis(2,4-dimethylvaleronitrile),dimethyl-2,2-azobis(2-methylpropionate), benzoyl peroxide, and lauroylperoxide. Polymerization is preferably effected while heating at 50 to80° C. The reaction time is usually about 2 to 100 hours, preferablyabout 5 to 20 hours. Aqueous ammonia, triethylamine or the like may beused as the base for the alkaline hydrolysis. For the alkalinehydrolysis, the temperature is usually −20° C. to 100° C., preferably 0°C. to 60° C., and the time is about 0.2 to 100 hours, preferably about0.5 to 20 hours.

Also included are polymers having the dendritic or hyperbranched polymerstructure of formula (2′″) below.

Herein ZZ is a divalent organic group selected from among CH₂, CH(OH),CR²(OH), C═O and C(OR²)(OH) or a trivalent organic group represented by—C(OH)═. Subscript F, which may be identical or different, is a positiveinteger, and H is a positive integer, satisfying 0.001≦H/(H+F)≦0.1, andXX is 1 or 2. R¹, R², x and y are as defined above.

The dendritic or hyperbranched polymer of phenol derivative can besynthesized by effecting living anion polymerization of a polymerizablemonomer such as 4-tert-butoxystyrene and reacting a branching monomersuch as chloromethylstyrene as appropriate during the living anionpolymerization.

More particularly, living anion polymerization is started using apolymerizable monomer such as 4-tert-butoxystyrene. After apredetermined amount has been polymerized, a branching monomer such aschloromethylstyrene is introduced and reacted with the intermediate.Then the polymerizable monomer such as 4-tert-butoxystyrene and/or thebranching monomer such as chloromethylstyrene is added again forpolymerization. This operation is repeated many times until a desireddendritic or hyperbranched polymer is obtained. If necessary, theprotective groups used to enable living polymerization are deprotected,yielding a dendritic or hyperbranched polymer of phenol derivative.

Examples of the branching monomer are given below.

R¹, R², x and y are as defined above.

Illustrative examples of the dendritic or hyperbranched polymer arethose having recurring units of the following approximate formulas (7)to (11).

Herein, broken lines (- - -) represent polymer chains derived from thephenol derivative monomer, and K represents units derived from thebranching monomer. The number of broken line segments between K and K isdepicted merely for the sake of convenience, independent of the numberof recurring units in the polymer chain included between K and K.

The dendritic or hyperbranched polymer of a phenol derivative isprepared by effecting living polymerization of the phenol derivative,reacting with a compound having a polymerizable moiety and a terminatingmoiety and proceeding further polymerization. By repeating thisoperation desired times, a dendritic or hyperbranched polymer of phenolderivative can be synthesized. The living polymerization may be effectedby any desired technique although living anion polymerization ispreferred because of ease of control. For the detail of synthesis,reference is made to JP-A 2000-344836.

The alkali-soluble resins or polymers should preferably have a weightaverage molecular weight (Mw) of 3,000 to 100,000, as measured by gelpermeation chromatography (GPC) versus polystyrene standards. Manypolymers with Mw of less than 3,000 do not perform well and are poor inheat resistance and film formation. Many polymers with Mw of more than100,000 give rise to a problem with respect to dissolution in the resistsolvent and developer. The polymer should also preferably have adispersity (Mw/Mn) of up to 3.5, and more preferably up to 1.5. With adispersity of more than 3.5, resolution is low in many cases. Althoughthe preparation method is not critical, a poly(p-hydroxystyrene) orsimilar polymer with a low dispersity or narrow dispersion can besynthesized by living anion polymerization.

In the resist composition of the invention, a resin having suchsubstituent groups with C—O—C linkages (acid labile groups) that thesolubility in an alkaline developer changes as a result of scission ofthe C—O—C linkages under the action of an acid, especially analkali-soluble resin as mentioned above is preferably used as component(A). Especially preferred is a polymer comprising recurring units of theabove formula (2) and containing phenolic hydroxyl groups in whichhydrogen atoms of the phenolic hydroxyl groups are substituted with acidlabile groups of one or more types in a proportion of more than 0 mol %to 80 mol % on the average of the entire hydrogen atoms of the phenolichydroxyl group, the polymer having a weight average molecular weight of3,000 to 100,000.

Also preferred is a polymer comprising recurring units of the aboveformula (2′), that is, a copolymer comprising p-hydroxystyrene and/orα-methyl-p-hydroxystyrene and acrylic acid and/or methacrylic acid,wherein some of the hydrogen atoms of the carboxyl groups of acrylicacid and/or methacrylic acid are substituted with acid labile groups ofone or more types, and the units derived from acrylate and/ormethacrylate are contained in a proportion of more than 0 mol % to 50mol %, on the average, of the copolymer, and wherein some of thehydrogen atoms of the phenolic hydroxyl groups of p-hydroxystyreneand/or α-methyl-p-hydroxystyrene may be substituted with acid labilegroups of one or more types. In the preferred copolymer, the unitsderived from acrylate and/or methacrylate and from p-hydroxystyreneand/or α-methyl-p-hydroxystyrene having acid labile groups substitutedthereon are contained in a proportion of more than 0 mol % to 80 mol %,on the average, of the copolymer.

Alternatively, a polymer comprising recurring units of the above formula(2″), that is, a copolymer comprising p-hydroxystyrene and/orα-methyl-p-hydroxystyrene and substituted and/or unsubstituted indene,is preferred wherein some of the hydrogen atoms of the phenolic hydroxylgroups on p-hydroxystyrene and/or α-methyl-p-hydroxystyrene aresubstituted with acid labile groups of one or more types, and/or some ofthe hydrogen atoms of the carboxyl groups on acrylic acid and/ormethacrylic acid are substituted with acid labile groups of one or moretypes. Where the substituted indene has hydroxyl groups, some of thehydrogen atoms of these hydroxyl groups may be substituted with acidlabile groups of one or more types. In the preferred copolymer, theunits derived from p-hydroxystyrene and/or α-methyl-p-hydroxystyrenehaving acid labile groups substituted thereon, the units derived fromacrylic acid and/or methacrylic acid having acid labile groupssubstituted thereon, and the units derived from indene having acidlabile groups substituted thereon are contained in a proportion of morethan 0 mol % to 80 mol %, on the average, of the copolymer.

Exemplary and preferred such polymers are polymers or high molecularweight compounds comprising recurring units represented by the followinggeneral formula (2a), (2a′) or (2a″) and having a weight averagemolecular weight of 3,000 to 100,000.

Herein, R¹ is hydrogen or methyl. R² is a straight, branched or cyclicalkyl group of 1 to 8 carbon atoms. Letter x is 0 or a positive integer,and y is a positive integer, satisfying x+y≦5. R³ is an acid labilegroup. S and T are positive integers, satisfying 0<T/(S+T)≦0.8. R^(3a)is hydrogen or an acid labile group, at least some of the R^(3a) groupsare acid labile groups. M and N are positive integers, L is 0 or apositive integer, satisfying 0<N/(M+N+L)≦0.5 and 0<(N+L)/(M+N+L)≦0.8.The letter yy is 0 or a positive integer, satisfying x+yy≦4. A and B arepositive integers, C, D and E each are 0 or a positive integer,satisfying 0<(B+E)/(A+B+C+D+E)≦0.5 and 0<(C+D+E)/(A+B+C+D+E)≦0.8.

R² stands for straight, branched or cyclic C₁₋₈ alkyl groups, forexample, methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl,tert-butyl, cyclohexyl and cyclopentyl.

In the event some of phenolic hydroxyl groups or some or all of carboxylgroups on the alkali-soluble resin are protected with acid labilesubstituent groups represented by C—O—C linkage, the acid labile groupsare selected from a variety of such groups. The preferred acid labilegroups are groups of the following general formulae (3) to (6), tertiaryalkyl groups of 4 to 20 carbon atoms, preferably 4 to 15 carbon atoms,trialkylsilyl groups whose alkyl groups each have 1 to 6 carbon atoms,oxoalkyl groups of 4 to 20 carbon atoms, or aryl-substituted alkylgroups of 7 to 20 carbon atoms. Inter alia, tertiary alkyl groups of 4to 20 carbon atoms and groups of the following general formula (5) aremore preferred.

Herein R⁴ and R⁵ are independently hydrogen or straight, branched orcyclic alkyl groups of 1 to 18 carbon atoms, preferably 1 to 10 carbonatoms, for example, methyl, ethyl, propyl, isopropyl, n-butyl,sec-butyl, tert-butyl, cyclopentyl, cyclohexyl, 2-ethylhexyl andn-octyl. R⁶ is a monovalent hydrocarbon group of 1 to 18 carbon atoms,preferably 1 to 10 carbon atoms, which may have a hetero atom (e.g.,oxygen atom), for example, straight, branched or cyclic alkyl groups,and such groups in which some hydrogen atoms are substituted withhydroxyl, alkoxy, oxo, amino or alkylamino groups. Illustrative examplesof the substituted alkyl groups are given below.

A pair of R⁴ and R⁵, a pair of R⁴ and R⁶, or a pair of R⁵ and R⁶, takentogether, may form a ring. Each of R⁴, R⁵ and R⁶ is a straight orbranched alkylene group of 1 to 18 carbon atoms, preferably 1 to 10carbon atoms, when they form a ring.

R⁷ is a tertiary alkyl group of 4 to 20 carbon atoms, preferably 4 to 15carbon atoms, a trialkylsilyl group whose alkyl groups each have 1 to 6carbon atoms, an oxoalkyl group of 4 to 20 carbon atoms or a group offormula (3). Exemplary tertiary alkyl groups are tert-butyl, tert-amyl,1,1-diethylpropyl, 1-ethylcyclopentyl, 1-butylcyclopentyl,1-ethylcyclohexyl, 1-butylcyclohexyl, 1-ethyl-2-cyclopentenyl,1-ethyl-2-cyclohexenyl, 2-methyl-2-adamantyl, 2-ethyl-2-adamantyl and1-adamantyl-1-methylethyl. Exemplary trialkylsilyl groups aretrimethylsilyl, triethylsilyl, and dimethyl-tert-butylsilyl. Exemplaryoxoalkyl groups are 3-oxocyclohexyl, 4-methyl-2-oxooxan-4-yl, and5-methyl-5-oxooxolan-4-yl. Letter z is an integer of 0 to 6.

R⁸ is a straight, branched or cyclic alkyl group of 1 to 8 carbon atomsor substituted or unsubstituted aryl group of 6 to 20 carbon atoms.Exemplary straight, branched or cyclic alkyl groups include methyl,ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, tert-amyl,n-pentyl, n-hexyl, cyclopentyl, cyclohexyl, cyclopentylmethyl,cyclopentylethyl, cyclohexylmethyl and cyclohexylethyl. Exemplarysubstituted or unsubstituted aryl groups include phenyl, methylphenyl,naphthyl, anthryl, phenanthryl, and pyrenyl. Letter h is equal to 0 or1, i is equal to 0, 1, 2 or 3, satisfying 2h+i=2 or 3.

R⁹ is a straight, branched or cyclic alkyl group of 1 to 8 carbon atomsor substituted or unsubstituted aryl group of 6 to 20 carbon atoms,examples of which are as exemplified for R⁸. R¹⁰ to R¹⁹ areindependently hydrogen or monovalent hydrocarbon groups of 1 to 15carbon atoms which may contain a hetero atom, for example, straight,branched or cyclic alkyl groups such as methyl, ethyl, propyl,isopropyl, n-butyl, sec-butyl, tert-butyl, tert-amyl, n-pentyl, n-hexyl,n-octyl, n-nonyl, n-decyl, cyclopentyl, cyclohexyl, cyclopentylmethyl,cyclopentylethyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl,and cyclohexylbutyl, and substituted ones of these groups in which somehydrogen atoms are substituted by hydroxyl, alkoxy, carboxy,alkoxycarbonyl, oxo, amino, alkylamino, cyano, mercapto, alkylthio, andsulfo groups. Any two of R¹⁰ to R¹⁹, for example, a pair of R¹⁰ and R¹¹,a pair of R¹⁰ and R¹², a pair of R¹¹ and R¹³, a pair of R¹² and R¹³, apair of R¹⁴ and R¹⁵, or a pair of R¹⁶ and R¹⁷, taken together, may forma ring. When any two of R¹⁰ to R¹⁹ form a ring, each is a divalenthydrocarbon group of 1 to 15 carbon atoms which may contain a heteroatom, examples of which are the above-exemplified monovalent hydrocarbongroups with one hydrogen atom eliminated. Also, two of R¹⁰ to R¹⁹ whichare attached to adjacent carbon atoms (for example, a pair of R¹⁰ andR¹², a pair of R¹² and R¹⁸, or a pair of R¹⁶ and R¹⁸) may directly bondtogether to form a double bond.

Of the acid labile groups of formula (3), illustrative examples of thestraight or branched groups are given below.

Of the acid labile groups of formula (3), illustrative examples of thecyclic groups include tetrahydrofuran-2-yl,2-methyltetrahydrofuran-2-yl, tetrahydropyran-2-yl and2-methyltetrahydropyran-2-yl.

Illustrative examples of the acid labile groups of formula (4) includetert-butoxycarbonyl, tert-butoxycarbonylmethyl, tert-amyloxycarbonyl,tert-amyloxycarbonylmethyl, 1,1-diethylpropyloxycarbonyl,1,1-diethylpropyloxycarbonylmethyl, 1-ethylcyclopentyloxycarbonyl,1-ethylcyclopentyloxycarbonylmethyl, 1-ethyl-2-cyclopentenyloxycarbonyl,1-ethyl-2-cyclopentenyloxycarbonylmethyl, 1-ethoxyethoxycarbonylmethyl,2-tetrahydropyranyloxycarbonylmethyl, and2-tetrahydrofuranyloxycarbonylmethyl.

Illustrative examples of the acid labile groups of formula (5) include1-methylcyclopentyl, 1-ethylcyclopentyl, 1-n-propylcyclopentyl,1-isopropylcyclopentyl, 1-n-butylcyclopentyl, 1-sec-butylcyclopentyl,1-methylcyclohexyl, 1-ethylcyclohexyl, 3-methyl-1-cyclopenten-3-yl,3-ethyl-1-cyclopenten-3-yl, 3-methyl-1-cyclohexen-3-yl,3-ethyl-1-cyclohexen-3-yl, and 1-cyclohexyl-cyclopentyl.

Illustrative examples of the acid labile groups of formula (6) are givenbelow.

Exemplary of the tertiary alkyl group of 4 to 20 carbon atoms,preferably 4 to 15 carbon atoms, are tert-butyl, tert-amyl,1,1-diethylpropyl, 1-ethylcyclopentyl, 1-butylcyclopentyl,1-ethylcyclohexyl, 1-butylcyclohexyl, 1-ethyl-2-cyclopentenyl,1-ethyl-2-cyclohexenyl, 2-methyl-2-adamantyl, 2-ethyl-2-adamantyl,1-adamantyl-1-methyl-ethyl.

Exemplary of the trialkylsilyl groups whose alkyl groups each have 1 to6 carbon atoms are trimethylsilyl, triethylsilyl, andtert-butyldimethylsilyl.

Exemplary of the oxoalkyl groups of 4 to 20 carbon atoms are3-oxocyclohexyl and groups represented by the following formulae.

Exemplary of the aryl-substituted alkyl groups of 7 to 20 carbon atomsare benzyl, methylbenzyl, dimethylbenzyl, diphenylmethyl, and1,1-diphenylethyl.

In the resist composition comprising the O-arenesulfonyloxime compoundas a photoacid generator, the resin (A) which changes its solubility inan alkaline developer under the action of an acid may also be a polymerof formula (2) or (2′), (2″) or (2′″) in which some of the hydrogenatoms of the phenolic hydroxyl groups are crosslinked within a moleculeand/or between molecules, in a proportion of more than 0 mol % to 50 mol%, on the average, of the entire phenolic hydroxyl groups on thepolymer, with crosslinking groups having C—O—C linkages represented bythe following general formula (12). With respect to illustrativeexamples and synthesis of polymers crosslinked with acid labile groups,reference should be made to JP-A 11-190904.

Herein, each of R²⁰ and R²¹ is hydrogen or a straight, branched orcyclic alkyl group of 1 to 8 carbon atoms, or R²⁰ and R²¹, takentogether, may form a ring, and each of R²⁰ and R²¹ is a straight orbranched alkylene group of 1 to 8 carbon atoms when they form a ring.R²² is a straight, branched or cyclic alkylene group of 1 to 10 carbonatoms. Letter “b” is 0 or an integer of 1 to 10. AA is an a-valentaliphatic or alicyclic saturated hydrocarbon group, aromatic hydrocarbongroup or heterocyclic group of 1 to 50 carbon atoms, which may beseparated by a hetero atom and in which some of the hydrogen atomattached to carbon atoms may be substituted by hydroxyl, carboxyl,carbonyl or halogen. Letter “a” is an integer of 1 to 7, especially 1 to3.

Preferably in formula (12), R²⁰ is methyl, R²¹ is hydrogen, a is 1, b is0, and AA is ethylene, 1,4-butylene or 1,4-cyclohexylene.

It is noted that these polymers which are crosslinked within themolecule or between molecules with crosslinking groups having C—O—Clinkages can be synthesized by reacting a corresponding non-crosslinkedpolymer with an alkenyl ether in the presence of an acid catalyst in aconventional manner.

If decomposition of other acid labile groups proceeds under acidcatalyst conditions, the end product can be obtained by once reactingthe alkenyl ether with hydrochloric acid or the like for conversion to ahalogenated alkyl ether and reacting it with the polymer under basicconditions in a conventional manner.

Illustrative, non-limiting, examples of the alkenyl ether includeethylene glycol divinyl ether, triethylene glycol divinyl ether,1,2-propanediol divinyl ether, 1,3-propanediol divinyl ether,1,3-butanediol divinyl ether, 1,4-butanediol divinyl ether, neopentylglycol divinyl ether, trimethylolpropane trivinyl ether,trimethylolethane trivinyl ether, hexanediol divinyl ether, and1,4-cyclohexanediol divinyl ether.

In the chemically amplified resist composition of the invention, theresin used as component (A) is as described above while the preferredacid labile groups to be substituted for phenolic hydroxyl groups are1-ethoxyethyl, 1-ethoxypropyl, tetrahydrofuranyl, tetrahydropyranyl,tert-butyl, tert-amyl, 1-ethylcyclohexyloxycarbonylmethyl,tert-butoxycarbonyl, tert-butoxycarbonylmethyl, and substituents offormula (12) wherein R²⁰ is methyl, R²¹ is hydrogen, a is 1, b is 0, andAA is ethylene, 1,4-butylene or 1,4-cyclohexylene. Also preferably, thehydrogen atoms of carboxyl groups on methacrylic acid or acrylic acidare protected with substituent groups as typified by tert-butyl,tert-amyl, 2-methyl-2-adamantyl, 2-ethyl-2-adamantyl,1-ethylcyclopentyl, 1-ethylcyclohexyl, 1-cyclohexylcyclopentyl,1-ethylnorbornyl, tetrahydrofuranyl and tetrahydropyranyl.

In a single polymer, these substituents may be incorporated alone or inadmixture of two or more types. A blend of two or more polymers havingsubstituents of different types is also acceptable.

The percent proportion of these substituents substituting for phenol andcarboxyl groups in the polymer is not critical. Preferably the percentsubstitution is selected such that when a resist composition comprisingthe polymer is applied onto a substrate to form a coating, the unexposedarea of the coating may have a dissolution rate of 0.01 to 10 Å/sec in a2.38% tetramethylammonium hydroxide (TMAH) developer.

On use of a polymer containing a greater proportion of carboxyl groupswhich can reduce the alkali dissolution rate, the percent substitutionmust be increased or non-acid-decomposable substituents to be describedlater must be introduced.

When acid labile groups for intramolecular and/or intermolecularcrosslinking are to be introduced, the percent proportion ofcrosslinking substituents is preferably up to 20 mol %, more preferablyup to 10 mol %, on the average, based on the entire recurring units ofthe polymer. If the percent substitution of crosslinking substituents istoo high, crosslinking results in a higher molecular weight which canadversely affect dissolution, stability and resolution. It is alsopreferred to further introduce another non-crosslinking acid labilegroup into the crosslinked polymer at a percent substitution of up to 10mol %, on the average, for adjusting the dissolution rate to fall withinthe above range.

In the case of poly(p-hydroxystyrene), the optimum percent substitutiondiffers between a substituent having a strong dissolution inhibitoryaction such as a tert-butoxycarbonyl group and a substituent having aweak dissolution inhibitory action such as an acetal group although theoverall percent substitution is preferably 10 to 40 mol %, morepreferably 20 to 30 mol %, on the average, based on the entire recurringunits of the polymer.

Polymers having such acid labile groups introduced therein shouldpreferably have a weight average molecular weight (Mw) of 3,000 to100,000, as measured by GPC versus polystyrene standards. With a Mw ofless than 3,000, polymers would perform poorly and often lack heatresistance and film formability. Polymers with a Mw of more than 100,000would be less soluble in a developer and a resist solvent.

Where non-crosslinking acid labile groups are introduced, the polymershould preferably have a dispersity (Mw/Mn) of up to 3.5, preferably upto 1.5. A polymer with a dispersity of more than 3.5 often results in alow resolution. Where crosslinking acid labile groups are introduced,the starting alkali-soluble resin should preferably have a dispersity(Mw/Mn) of up to 1.5, and the dispersity is kept at 3 or lower evenafter protection with crosslinking acid labile groups. If the dispersityis higher than 3, dissolution, coating, storage stability and/orresolution is often poor.

To impart a certain function, suitable substituent groups may beintroduced into some of the phenolic hydroxyl and carboxyl groups on theacid labile group-protected polymer. Exemplary are substituent groupsfor improving adhesion to the substrate, non-acid-labile groups foradjusting dissolution in an alkali developer, and substituent groups forimproving etching resistance. Illustrative, non-limiting, substituentgroups include 2-hydroxyethyl, 2-hydroxypropyl, methoxymethyl,methoxycarbonyl, ethoxycarbonyl, methoxycarbonylmethyl,ethoxycarbonylmethyl, 4-methyl-2-oxo-4-oxolanyl,4-methyl-2-oxo-4-oxanyl, methyl, ethyl, propyl, n-butyl, sec-butyl,acetyl, pivaloyl, adamantyl, isoboronyl, and cyclohexyl.

Notably, the use of acid labile groups other than those of the acetaltype is preferred for reducing the top loss at the resist topconcomitant with a thickness reduction. Specifically, tertiary ethersand tertiary esters are preferred. For phenolic hydroxyl groups, suchsubstituent groups as tert-butyl, tert-amyl, and1-ethylcyclohexyloxycarbonylmethyl are preferably used. For hydrogenatoms of the carboxyl group on methacrylic acid or acrylic acid, suchsubstituent groups as tert-butyl, tert-amyl, 2-methyl-2-adamantyl,2-ethyl-2-adamantyl, 1-ethylcyclopentyl, 1-ethylcyclohexyl,1-cyclohexylcyclopentyl, and 1-ethylnorbornyl are desirable. Protectionwith these substituent groups is desired.

In the resist composition of the invention, the above-described resin isadded in any desired amount, and usually 65 to 99 parts by weight,preferably 65 to 98 parts by weight among 100 parts by weight of thesolids in the composition. The term “solids” is used to encompass allcomponents in the resist composition excluding the solvent.

With respect to component (B), illustrative examples of the photoacidgenerators of formulae (1) or (1a) are as described above.

In the chemically amplified resist composition, an appropriate amount ofthe photoacid generator added is from 0.1 part to 10 parts by weight,and preferably from 1 to 5 parts by weight, among 100 parts by weight ofthe solids in the composition. A less amount of the photoacid generatorbelow the range fails to generate a sufficient amount of acid todeprotect acid labile groups in the polymer. Too large amounts mayexcessively reduce the transmittance of resist film, failing to form arectangular pattern, and give rise to problems of abnormal particles anddeposits during resist storage. The photoacid generators may be usedalone or in admixture of two or more.

Component (C)

In one preferred embodiment, the resist composition further contains (C)a compound capable of generating an acid upon exposure to high-energyradiation (UV, deep UV, electron beams, x-rays, excimer laser beams,gamma-rays or synchrotron radiation), that is, a second photoacidgenerator other than component (B). Suitable second photoacid generatorsinclude sulfonium salts, iodonium salts, sulfonyldiazomethane andN-sulfonyloxydicarboxylmide photoacid generators. Exemplary secondphotoacid generators are given below while they may be used alone or inadmixture of two or more.

Sulfonium salts are salts of sulfonium cations with sulfonates,bis(substituted alkylsulfonyl)imides and tris(substitutedalkylsulfonyl)methides. Exemplary sulfonium cations includetriphenylsulfonium, (4-tert-butoxyphenyl)diphenylsulfonium,bis(4-tert-butoxyphenyl)phenylsulfonium,tris(4-tert-butoxyphenyl)sulfonium,(3-tert-butoxyphenyl)diphenylsulfonium,bis(3-tert-butoxyphenyl)phenylsulfonium,tris(3-tert-butoxyphenyl)sulfonium,(3,4-di-tert-butoxyphenyl)diphenylsulfonium,bis(3,4-di-tert-butoxyphenyl)phenylsulfonium,tris(3,4-di-tert-butoxyphenyl)sulfonium,diphenyl(4-thiophenoxyphenyl)sulfonium,(4-tert-butoxycarbonylmethyloxyphenyl)diphenylsulfonium,tris(4-tert-butoxycarbonylmethyloxyphenyl)sulfonium,(4-tert-butoxyphenyl)bis(4-dimethylaminophenyl)sulfonium,tris(4-dimethylaminophenyl)sulfonium, 4-methylphenyldiphenylsulfonium,4-tert-butylphenyldiphenylsulfonium, bis(4-methylphenyl)phenylsulfonium,bis(4-tert-butylphenyl)phenylsulfonium, tris(4-methylphenyl)sulfonium,tris(4-tert-butylphenyl)sulfonium, tris(phenylmethyl)sulfonium,2-naphthyldiphenylsulfonium, dimethyl-2-naphthylsulfonium,4-hydroxyphenyldimethylsulfonium, 4-methoxyphenyldimethylsulfonium,trimethylsulfonium, 2-oxocyclohexylcyclohexylmethylsulfonium,trinaphthylsulfonium, tribenzylsulfonium, diphenylmethylsulfonium,dimethylphenylsulfonium, 2-oxopropylthiacyclopentanium,2-oxobutylthiacyclopentanium, 2-oxo-3,3-dimethylbutylthiacyclopentanium,2-oxo-2-phenylethylthiacyclopentanium,4-n-butoxynaphthyl-1-thiacyclopentanium, and2-n-butoxynaphthyl-1-thiacyclopentanium. Exemplary sulfonates includetrifluoromethanesulfonate, pentafluoroethanesulfonate,heptafluoropropanesulfonate, nonafluorobutanesulfonate,dodecafluorohexanesulfonate,pentafluoroethylperfluorocyclohexanesulfonate,heptadecafluorooctanesulfonate, perfluoro-4-ethylcyclohexanesulfonate,2,2,2-trifluoroethanesulfonate, pentafluorobenzenesulfonate,4-trifluoromethylbenzenesulfonate, 4-fluorobenzenesulfonate,mesitylenesulfonate, 2,4,6-triisopropylbenzenesulfonate,toluenesulfonate, benzenesulfonate,4-(4′-toluenesulfonyloxy)benzenesulfonate,6-(4-toluenesulfonyloxy)naphthalene-2-sulfonate,4-(4-toluenesulfonyloxy)naphthalene-1-sulfonate,5-(4-toluenesulfonyloxy)naphthalene-1-sulfonate,8-(4-toluenesulfonyloxy)naphthalene-1-sulfonate, naphthalenesulfonate,camphorsulfonate, octanesulfonate, dodecylbenzenesulfonate,butanesulfonate, methanesulfonate,1,1-difluoro-2-naphthyl-ethanesulfonate,1,1,2,2-tetrafluoro-2-(norbornan-2-yl)ethanesulfonate, and1,1,2,2-tetrafluoro-2-(tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-en-8-yl)ethanesulfonate.Exemplary bis(substituted alkylsulfonyl)imides includebistrifluoromethylsulfonylimide, bispentafluoroethylsulfonylimide,bisheptafluoropropylsulfonylimide, and 1,3-propylenebissulfonylimide. Atypical tris(substituted alkylsulfonyl)methide istristrifluoromethylsulfonylmethide. Sulfonium salts based on combinationof the foregoing examples are included.

Iodonium salts are salts of iodonium cations with sulfonates,bis(substituted alkylsulfonyl)imides and tris(substitutedalkylsulfonyl)methides. Exemplary iodonium cations are aryliodoniumcations including diphenyliodinium, bis(4-tert-butylphenyl)iodonium,4-tert-butoxyphenylphenyliodonium, and 4-methoxyphenylphenyliodonium.Exemplary sulfonates include trifluoromethanesulfonate,pentafluoroethanesulfonate, heptafluoropropanesulfonate,nonafluorobutanesulfonate, dodecafluorohexanesulfonate,pentafluoroethylperfluorocyclohexanesulfonate,heptadecafluorooctanesulfonate, perfluoro-4-ethylcyclohexanesulfonate,2,2,2-trifluoroethanesulfonate, pentafluorobenzenesulfonate,4-trifluoromethylbenzenesulfonate, 4-fluorobenzenesulfonate,mesitylenesulfonate, 2,4,6-triisopropylbenzenesulfonate,toluenesulfonate, benzenesulfonate,4-(4′-toluenesulfonyloxy)benzenesulfonate,6-(4-toluenesulfonyloxy)naphthalene-2-sulfonate,4-(4-toluenesulfonyloxy)naphthalene-1-sulfonate,5-(4-toluenesulfonyloxy)naphthalene-1-sulfonate,8-(4-toluenesulfonyloxy)naphthalene-1-sulfonate, naphthalenesulfonate,camphorsulfonate, octanesulfonate, dodecylbenzenesulfonate,butanesulfonate, methanesulfonate,1,1-difluoro-2-naphthyl-ethanesulfonate,1,1,2,2-tetrafluoro-2-(norbornan-2-yl)ethanesulfonate, and1,1,2,2-tetrafluoro-2-(tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-en-8-yl)ethanesulfonate.Exemplary bis(substituted alkylsulfonyl)imides includebistrifluoromethylsulfonylimide, bispentafluoroethylsulfonylimide,bisheptafluoropropylsulfonylimide, and 1,3-propylenebissulfonylimide. Atypical tris(substituted alkylsulfonyl)methide istristrifluoromethylsulfonylmethide. Iodonium salts based on combinationof the foregoing examples are included.

Exemplary sulfonyldiazomethane compounds include bissulfonyldiazomethanecompounds and sulfonyl-carbonyldiazomethane compounds such asbis(ethylsulfonyl)diazomethane, bis(1-methylpropylsulfonyl)diazomethane,bis(2-methylpropylsulfonyl)diazomethane,bis(1,1-dimethylethylsulfonyl)diazomethane,bis(cyclohexylsulfonyl)diazomethane,bis(perfluoroisopropylsulfonyl)diazomethane,bis(phenylsulfonyl)diazomethane,bis(4-methylphenylsulfonyl)diazomethane,bis(2,4-dimethylphenylsulfonyl)diazomethane,bis(4-acetyloxyphenylsulfonyl)diazomethane,bis(4-methanesulfonyloxyphenylsulfonyl)diazomethane,bis(4-(4-toluenesulfonyloxy)phenylsulfonyl)diazomethane,bis(2-naphthylsulfonyl)diazomethane,4-methylphenylsulfonylbenzoyldiazomethane,tert-butylcarbonyl-4-methylphenylsulfonyldiazomethane,2-naphthylsulfonylbenzoyldiazomethane,4-methylphenylsulfonyl-2-naphthoyldiazomethane,methylsulfonylbenzoyldiazomethane, andtert-butoxycarbonyl-4-methylphenylsulfonyldiazomethane.

N-sulfonyloxyimide photoacid generators include combinations of imideskeletons with sulfonates. Exemplary imide skeletons are succinimide,naphthalenedicarboximide, phthalimide, cyclohexyldicarboximide,5-norbornene-2,3-dicarboximide, and7-oxabicyclo[2.2.1]-5-heptene-2,3-dicarboximide. Exemplary sulfonatesinclude trifluoromethanesulfonate, pentafluoroethanesulfonate,heptafluoropropanesulfonate, nonafluorobutanesulfonate,dodecafluorohexanesulfonate,pentafluoroethylperfluorocyclohexanesulfonate,heptadecafluorooctanesulfonate, 2,2,2-trifluoroethanesulfonate,pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate,4-fluorobenzenesulfonate, mesitylenesulfonate,2,4,6-triisopropylbenzenesulfonate, toluenesulfonate, benzenesulfonate,naphthalenesulfonate, camphorsulfonate, octanesulfonate,dodecylbenzenesulfonate, butanesulfonate, methanesulfonate,1,1-difluoro-2-naphthyl-ethanesulfonate,1,1,2,2-tetrafluoro-2-(norbornan-2-yl)ethanesulfonate, and1,1,2,2-tetrafluoro-2-(tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-en-8-yl)ethanesulfonate.

Benzoinsulfonate photoacid generators include benzoin tosylate, benzoinmesylate, and benzoin butanesulfonate.

Pyrogallol trisulfonate photoacid generators include pyrogallol,phloroglucinol, catechol, resorcinol, and hydroquinone, in which all thehydroxyl groups are substituted by trifluoromethanesulfonate,pentafluoroethanesulfonate, heptafluoropropanesulfonate,nonafluorobutanesulfonate, dodecafluorohexanesulfonate,pentafluoroethylperfluorocyclohexanesulfonate,heptadecafluorooctanesulfonate, 2,2,2-trifluoroethanesulfonate,pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate,4-fluorobenzenesulfonate, toluenesulfonate, benzenesulfonate,naphthalenesulfonate, camphorsulfonate, octanesulfonate,dodecylbenzenesulfonate, butanesulfonate, methanesulfonate,1,1-difluoro-2-naphthyl-ethanesulfonate,1,1,2,2-tetrafluoro-2-(norbornan-2-yl)ethanesulfonate, and1,1,2,2-tetrafluoro-2-(tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-en-8-yl)ethanesulfonate.

Nitrobenzyl sulfonate photoacid generators include 2,4-dinitrobenzylsulfonate, 2-nitrobenzyl sulfonate, and 2,6-dinitrobenzyl sulfonate,with exemplary sulfonates including trifluoromethanesulfonate,pentafluoroethanesulfonate, heptafluoropropanesulfonate,nonafluorobutanesulfonate, dodecafluorohexanesulfonate,pentafluoroethylperfluorocyclohexanesulfonate,heptadecafluorooctanesulfonate, 2,2,2-trifluoroethanesulfonate,pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate,4-fluorobenzenesulfonate, toluenesulfonate, benzenesulfonate,naphthalenesulfonate, camphorsulfonate, octanesulfonate,dodecylbenzenesulfonate, butanesulfonate, methanesulfonate,1,1-difluoro-2-naphthyl-ethanesulfonate,1,1,2,2-tetrafluoro-2-(norbornan-2-yl)ethanesulfonate, and1,1,2,2-tetrafluoro-2-(tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-en-8-yl)ethanesulfonate.Also useful are analogous nitrobenzyl sulfonate compounds in which thenitro group on the benzyl side is substituted by a trifluoromethylgroup.

Sulfone photoacid generators include bis(phenylsulfonyl)methane,bis(4-methylphenylsulfonyl)methane, bis(2-naphthylsulfonyl)methane,2,2-bis(phenylsulfonyl)propane, 2,2-bis(4-methylphenylsulfonyl)propane,2,2-bis(2-naphthylsulfonyl)propane,2-methyl-2-(p-toluenesulfonyl)propiophenone,2-cyclohexylcarbonyl-2-(p-toluenesulfonyl)propane, and2,4-dimethyl-2-(p-toluenesulfonyl)pentan-3-one.

Illustrative of the O-arenesulfonyloxime or O-alkylsulfonyloximecompound (oximesulfonate) are photoacid generators in the form ofglyoxime derivatives, typically the compounds described in JapanesePatent No. 2,906,999 and JP-A 9-301948; photoacid generators ofoximesulfonate type having a conjugated system extended via thiophene orcyclohexadiene, typically the compounds described in U.S. Pat. No.6,004,724; oximesulfonate compounds stabilized with electron withdrawinggroups such as trifluoromethyl groups, typically the compounds describedin U.S. Pat. No. 6,261,738, JP-A 2000-314956, and InternationalPublication 2004/074242; oximesulfonate compounds derived fromphenylacetonitrile and substituted acetonitriles, typically thecompounds described in JP-A 9-95479, JP-A 9-230588 and the referencescited therein; and bisoximesulfonate compounds, typically the compoundsdescribed in JP-A 9-208554, GB 2,348,644A, and JP-A 2002-278053.

When the second photoacid generator (C) is added to the resistcomposition for KrF excimer laser lithography, the preferred photoacidgenerators are sulfonium salts, bissulfonyldiazomethanes,N-sulfonyloxydicarboximides, and oximesulfonates. Illustrative preferredphotoacid generators include triphenylsulfonium p-toluenesulfonate,triphenylsulfonium camphorsulfonate, triphenylsulfoniumpentafluorobenzenesulfonate, triphenylsulfoniumnonafluorobutanesulfonate, triphenylsulfonium4-(4′-toluenesulfonyloxy)benzenesulfonate, triphenylsulfonium2,4,6-triisopropylbenzenesulfonate, 4-tert-butoxyphenyldiphenylsulfoniump-toluenesulfonate, 4-tert-butoxyphenyldiphenylsulfoniumcamphorsulfonate, 4-tert-butoxyphenyldiphenylsulfonium4-(4′-toluenesulfonyloxy)benzenesulfonate, tris(4-methylphenyl)sulfoniumcamphorsulfonate, tris(4-tert-butylphenyl)sulfonium camphorsulfonate,bis(tert-butylsulfonyl)diazomethane,bis(cyclohexylsulfonyl)diazomethane,bis(2,4-dimethylphenylsulfonyl)diazomethane,bis(4-tert-butylphenylsulfonyl)diazomethane,N-camphorsulfonyloxy-5-norbornene-2,3-carboximide,N-p-toluenesulfonyloxy-5-norbornene-2,3-carboximide,(5-(10-camphorsulfonyl)oximino-5H-thiophen-2-ylidene),(2-methylphenyl)acetonitrile,5-(4-toluenesulfonyl)oximino-5H-thiophen-2-ylidene, and(2-methylphenyl)acetonitrile.

In the resist composition comprising the O-arenesulfonyloxime compoundas the first photoacid generator (B) according to the invention, thesecond photoacid generator (C) may be used in any desired amount as longas it does not compromise the effects of the O-arenesulfonyloximecompound. An appropriate amount of the second photoacid generator (C) is0 to 10 parts, and especially 0 to 5 parts by weight among 100 parts byweight of the solids in the composition. Too high a proportion of thesecond photoacid generator (C) may give rise to problems of degradedresolution and foreign matter upon development and resist film peeling.The second photoacid generators may be used alone or in admixture of twoor more. The transmittance of the resist film can be controlled by usinga (second) photoacid generator having a low transmittance at theexposure wavelength and adjusting the amount of the photoacid generatoradded.

In the resist composition comprising the O-arenesulfonyloxime compoundas the photoacid generator according to the invention, there may beadded a compound which is decomposed with an acid to generate anotheracid, that is, acid-amplifier compound. For these compounds, referenceshould be made to J. Photopolym. Sci. and Tech., 8, 43-44, 45-46 (1995),and ibid., 9, 29-30 (1996).

Examples of the acid-amplifier compound includetert-butyl-2-methyl-2-tosyloxymethyl acetoacetate and2-phenyl-2-(2-tosyloxyethyl)-1,3-dioxolane, but are not limited thereto.Of well-known photoacid generators, many of those compounds having poorstability, especially poor thermal stability exhibit an acidamplifier-like behavior.

In the resist composition of the invention, an appropriate amount of theacid-amplifier compound is up to 2 parts, and especially up to 1 part byweight among 100 parts by weight of the solids in the composition.Excessive amounts of the acid-amplifier compound make diffusion controldifficult, leading to degradation of resolution and patternconfiguration.

Component (D)

The basic compound used as component (D) is preferably a compoundcapable of suppressing the rate of diffusion when the acid generated bythe photoacid generator diffuses within the resist film. The inclusionof this type of basic compound holds down the rate of acid diffusionwithin the resist film, resulting in better resolution. In addition, itsuppresses changes in sensitivity following exposure and reducessubstrate and environment dependence, as well as improving the exposurelatitude and the pattern profile.

Examples of basic compounds include primary, secondary, and tertiaryaliphatic amines, mixed amines, aromatic amines, heterocyclic amines,nitrogen-containing compounds having carboxyl group, nitrogen-containingcompounds having sulfonyl group, nitrogen-containing compounds havinghydroxyl group, nitrogen-containing compounds having hydroxyphenylgroup, alcoholic nitrogen-containing compounds, amide derivatives, andimide derivatives.

Examples of suitable primary aliphatic amines include ammonia,methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine,isobutylamine, sec-butylamine, tert-butylamine, pentylamine,tert-amylamine, cyclopentylamine, hexylamine, cyclohexylamine,heptylamine, octylamine, nonylamine, decylamine, dodecylamine,cetylamine, methylenediamine, ethylenediamine, andtetraethylenepentamine. Examples of suitable secondary aliphatic aminesinclude dimethylamine, diethylamine, di-n-propylamine, diisopropylamine,di-n-butylamine, diisobutylamine, di-sec-butylamine, dipentylamine,dicyclopentylamine, dihexylamine, dicyclohexylamine, diheptylamine,dioctylamine, dinonylamine, didecylamine, didodecylamine, dicetylamine,N,N-dimethylmethylenediamine, N,N-dimethylethylenediamine, andN,N-dimethyltetraethylenepentamine. Examples of suitable tertiaryaliphatic amines include trimethylamine, triethylamine,tri-n-propylamine, triisopropylamine, tri-n-butylamine,triisobutylamine, tri-sec-butylamine, tripentylamine,tricyclopentylamine, trihexylamine, tricyclohexylamine, triheptylamine,trioctylamine, trinonylamine, tridecylamine, tridodecylamine,tricetylamine, N,N,N′,N′-tetramethylmethylenediamine,N,N,N′,N′-tetramethylethylenediamine, andN,N,N′,N′-tetramethyltetraethylenepentamine.

Examples of suitable mixed amines include dimethylethylamine,methylethylpropylamine, benzylamine, phenethylamine, andbenzyldimethylamine. Examples of suitable aromatic and heterocyclicamines include aniline derivatives (e.g., aniline, N-methylaniline,N-ethylaniline, N-propylaniline, N,N-dimethylaniline, 2-methylaniline,3-methylaniline, 4-methylaniline, ethylaniline, propylaniline,trimethylaniline, 2-nitroaniline, 3-nitroaniline, 4-nitroaniline,2,4-dinitroaniline, 2,6-dinitroaniline, 3,5-dinitroaniline, andN,N-dimethyltoluidine), diphenyl(p-tolyl)amine, methyldiphenylamine,triphenylamine, phenylenediamine, naphthylamine, diaminonaphthalene,pyrrole derivatives (e.g., pyrrole, 2H-pyrrole, 1-methylpyrrole,2,4-dimethylpyrrole, 2,5-dimethylpyrrole, and N-methylpyrrole), oxazolederivatives (e.g., oxazole and isooxazole), thiazole derivatives (e.g.,thiazole and isothiazole), imidazole derivatives (e.g., imidazole,4-methylimidazole, and 4-methyl-2-phenylimidazole), pyrazolederivatives, furazan derivatives, pyrroline derivatives (e.g., pyrrolineand 2-methyl-1-pyrroline), pyrrolidine derivatives (e.g., pyrrolidine,N-methylpyrrolidine, pyrrolidinone, and N-methylpyrrolidone),imidazoline derivatives, imidazolidine derivatives, pyridine derivatives(e.g., pyridine, methylpyridine, ethylpyridine, propylpyridine,butylpyridine, 4-(1-butylpentyl)pyridine, dimethylpyridine,trimethylpyridine, triethylpyridine, phenylpyridine,3-methyl-2-phenylpyridine, 4-tert-butylpyridine, diphenylpyridine,benzylpyridine, methoxypyridine, butoxypyridine, dimethoxypyridine,1-methyl-2-pyridine, 4-pyrrolidinopyridine, 1-methyl-4-phenylpyridine,2-(1-ethylpropyl)pyridine, aminopyridine, and dimethylaminopyridine),pyridazine derivatives, pyrimidine derivatives, pyrazine derivatives,pyrazoline derivatives, pyrazolidine derivatives, piperidinederivatives, piperazine derivatives, morpholine derivatives, indolederivatives, isoindole derivatives, 1H-indazole derivatives, indolinederivatives, quinoline derivatives (e.g., quinoline and3-quinolinecarbonitrile), isoquinoline derivatives, cinnolinederivatives, quinazoline derivatives, quinoxaline derivatives,phthalazine derivatives, purine derivatives, pteridine derivatives,carbazole derivatives, phenanthridine derivatives, acridine derivatives,phenazine derivatives, 1,10-phenanthroline derivatives, adeninederivatives, adenosine derivatives, guanine derivatives, guanosinederivatives, uracil derivatives, and uridine derivatives.

Examples of suitable nitrogen-containing compounds having carboxyl groupinclude aminobenzoic acid, indolecarboxylic acid, and amino acidderivatives (e.g. nicotinic acid, alanine, alginine, aspartic acid,glutamic acid, glycine, histidine, isoleucine, glycylleucine, leucine,methionine, phenylalanine, threonine, lysine,3-aminopyrazine-2-carboxylic acid, and methoxyalanine). Examples ofsuitable nitrogen-containing compounds having sulfonyl group include3-pyridinesulfonic acid and pyridinium p-toluenesulfonate. Examples ofsuitable nitrogen-containing compounds having hydroxyl group,nitrogen-containing compounds having hydroxyphenyl group, and alcoholicnitrogen-containing compounds include 2-hydroxypyridine, aminocresol,2,4-quinolinediol, 3-indolemethanol hydrate, monoethanolamine,diethanolamine, triethanolamine, N-ethyldiethanolamine,N,N-diethylethanolamine, triisopropanolamine, 2,2′-iminodiethanol,2-aminoethanol, 3-amino-1-propanol, 4-amino-1-butanol,4-(2-hydroxyethyl)morpholine, 2-(2-hydroxyethyl)pyridine,1-(2-hydroxyethyl)piperazine, 1-[2-(2-hydroxyethoxy)ethyl]piperazine,piperidine ethanol, 1-(2-hydroxyethyl)pyrrolidine,1-(2-hydroxyethyl)-2-pyrrolidinone, 3-piperidino-1,2-propanediol,3-pyrrolidino-1,2-propanediol, 8-hydroxyjulolidine, 3-quinuclidinol,3-tropanol, 1-methyl-2-pyrrolidine ethanol, 1-aziridine ethanol,N-(2-hydroxyethyl)phthalimide, and N-(2-hydroxyethyl)isonicotinamide.Examples of suitable amide derivatives include formamide,N-methylformamide, N,N-dimethylformamide, acetamide, N-methylacetamide,N,N-dimethylacetamide, propionamide, and benzamide. Suitable imidederivatives include phthalimide, succinimide, and maleimide.

In addition, basic compounds of the following general formula (D1) mayalso be included alone or in admixture.N(X′)_(w)(Y)_(3-w)  (D1)

In the formula, w is equal to 1, 2 or 3; Y is independently hydrogen ora straight, branched or cyclic alkyl group of 1 to 20 carbon atoms whichmay contain a hydroxyl group or ether structure; and X′ is independentlyselected from groups of the following general formulas (X′1) to (X′3),and two or three X′ may bond together to form a ring.

In the formulas, R³⁰⁰, R³⁰² and R³⁰⁵ are independently straight orbranched alkylene groups of 1 to 4 carbon at oms; R³⁰¹, R³⁰⁴ and R³⁰⁶are independently hydrogen, straight, branched or cyclic alkyl groups of1 to 20 carbon atoms, which may contain at least one hydroxyl group,ether structure, ester structure or lactone ring; and R³⁰³ is a singlebond or a straight or branched alkylene group of 1 to 4 carbon atoms.

Illustrative examples of the basic compounds of formula (D1) includetris(2-methoxymethoxyethyl)amine, tris{2-(2-methoxyethoxy)ethyl}amine,tris{2-(2-methoxyethoxymethoxy)ethyl}amine,tris{2-(1-methoxyethoxy)ethyl}amine, tris{2-(1-ethoxyethoxy)ethyl}amine,tris{2-(1-ethoxypropoxy)ethyl}amine,tris[2-{2-(2-hydroxyethoxy)ethoxy}ethyl]amine,4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane,4,7,13,18-tetraoxa-1,10-diazabicyclo[8.5.5]eicosane,1,4,10,13-tetraoxa-7,16-diazabicyclooctadecane, 1-aza-12-crown-4,1-aza-15-crown-5, 1-aza-18-crown-6, tris(2-formyloxyethyl)amine,tris(2-acetoxyethyl)amine, tris(2-propionyloxyethyl)amine,tris(2-butyryloxyethyl)amine, tris(2-isobutyryloxyethyl)amine,tris(2-valeryloxyethyl)amine, tris(2-pivaloyloxyethyl)amine,N,N-bis(2-acetoxyethyl)-2-(acetoxyacetoxy)ethylamine,tris(2-methoxycarbonyloxyethyl)amine,tris(2-tert-butoxycarbonyloxyethyl)amine,tris[2-(2-oxopropoxy)ethyl]amine,tris[2-(methoxycarbonylmethyl)oxyethyl]amine,tris[2-(tert-butoxycarbonylmethyloxy)ethyl]amine,tris[2-(cyclohexyloxycarbonylmethyloxy)ethyl]amine,tris(2-methoxycarbonylethyl)amine, tris(2-ethoxycarbonylethyl)amine,N,N-bis(2-hydroxyethyl)-2-(methoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(methoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(ethoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(ethoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(2-methoxyethoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(2-methoxyethoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(2-hydroxyethoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(2-acetoxyethoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-[(methoxycarbonyl)methoxycarbonyl]-ethylamine,N,N-bis(2-acetoxyethyl)-2-[(methoxycarbonyl)methoxycarbonyl]-ethylamine,N,N-bis(2-hydroxyethyl)-2-(2-oxopropoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(2-oxopropoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(tetrahydrofurfuryloxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(tetrahydrofurfuryloxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-[(2-oxotetrahydrofuran-3-yl)oxy-carbonyl]ethylamine,N,N-bis(2-acetoxyethyl)-2-[(2-oxotetrahydrofuran-3-yl)oxy-carbonyl]ethylamine,N,N-bis(2-hydroxyethyl)-2-(4-hydroxybutoxycarbonyl)ethylamine,N,N-bis(2-formyloxyethyl)-2-(4-formyloxybutoxycarbonyl)ethylamine,N,N-bis(2-formyloxyethyl)-2-(2-formyloxyethoxycarbonyl)ethylamine,N,N-bis(2-methoxyethyl)-2-(methoxycarbonyl)ethylamine,N-(2-hydroxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(2-acetoxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(2-hydroxyethyl)-bis[2-(ethoxycarbonyl)ethyl]amine,N-(2-acetoxyethyl)-bis[2-(ethoxycarbonyl)ethyl]amine,N-(3-hydroxy-1-propyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(3-acetoxy-1-propyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(2-methoxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-butyl-bis[2-(methoxycarbonyl)ethyl]amine,N-butyl-bis[2-(2-methoxyethoxycarbonyl)ethyl]amine,N-methyl-bis(2-acetoxyethyl)amine, N-ethyl-bis(2-acetoxyethyl)amine,N-methyl-bis(2-pivaloyloxyethyl)amine,N-ethyl-bis[2-(methoxycarbonyloxy)ethyl]amine,N-ethyl-bis[2-(tert-butoxycarbonyloxy)ethyl]amine,tris(methoxycarbonylmethyl)amine, tris(ethoxycarbonylmethyl)amine,N-butyl-bis(methoxycarbonylmethyl)amine,N-hexyl-bis(methoxycarbonylmethyl)amine, andβ-(diethylamino)-δ-valerolactone.

Also useful are one or more of cyclic structure-bearing basic compoundshaving the following general formula (D2).

Herein X′ is as defined above, and R³⁰⁷ is a straight or branchedalkylene group of 2 to 20 carbon atoms which may contain one or morecarbonyl groups, ether structures, ester structures or sulfidestructures.

Illustrative examples of the cyclic structure-bearing basic compoundshaving formula (D2) include 1-[2-(methoxymethoxy)ethyl]pyrrolidine,1-[2-(methoxymethoxy)ethyl]piperidine,4-[2-(methoxymethoxy)ethyl]morpholine,1-[2-[(2-methoxyethoxy)methoxy]ethyl]pyrrolidine,1-[2-[(2-methoxyethoxy)methoxy]ethyl]piperidine,4-[2-[(2-methoxyethoxy)methoxy]ethyl]morpholine, 2-(1-pyrrolidinyl)ethylacetate, 2-piperidinoethyl acetate, 2-morpholinoethyl acetate,2-(1-pyrrolidinyl)ethyl formate, 2-piperidinoethyl propionate,2-morpholinoethyl acetoxyacetate, 2-(1-pyrrolidinyl)ethylmethoxyacetate, 4-[2-(methoxycarbonyloxy)ethyl]morpholine,1-[2-(t-butoxycarbonyloxy)ethyl]piperidine,4-[2-(2-methoxyethoxycarbonyloxy)ethyl]morpholine, methyl3-(1-pyrrolidinyl)propionate, methyl 3-piperidinopropionate, methyl3-morpholinopropionate, methyl 3-(thiomorpholino)propionate, methyl2-methyl-3-(1-pyrrolidinyl)propionate, ethyl 3-morpholinopropionate,methoxycarbonylmethyl 3-piperidinopropionate, 2-hydroxyethyl3-(1-pyrrolidinyl)propionate, 2-acetoxyethyl 3-morpholinopropionate,2-oxotetrahydrofuran-3-yl 3-(1-pyrrolidinyl)propionate,tetrahydrofurfuryl 3-morpholinopropionate, glycidyl3-piperidinopropionate, 2-methoxyethyl 3-morpholinopropionate,2-(2-methoxyethoxy)ethyl 3-(1-pyrrolidinyl)propionate, butyl3-morpholinopropionate, cyclohexyl 3-piperidinopropionate,α-(1-pyrrolidinyl)methyl-γ-butyrolactone, β-piperidino-γ-butyrolactone,β-morpholino-δ-valerolactone, methyl 1-pyrrolidinylacetate, methylpiperidinoacetate, methyl morpholinoacetate, methylthiomorpholinoacetate, ethyl 1-pyrrolidinylacetate, and 2-methoxyethylmorpholinoacetate.

Also, one or more of cyano-bearing basic compounds having the followinggeneral formulae (D3) to (D6) may be blended.

Herein, X′, R³⁰⁷ and w are as defined above, and R³⁰⁸ and R³⁰⁹ each areindependently a straight or branched alkylene group of 1 to 4 carbonatoms.

Illustrative examples of the cyano-bearing basic compounds havingformulae (D3) to (D6) include 3-(diethylamino)propiononitrile,N,N-bis(2-hydroxyethyl)-3-aminopropiononitrile,N,N-bis(2-acetoxyethyl)-3-aminopropiononitrile,N,N-bis(2-formyloxyethyl)-3-aminopropiononitrile,N,N-bis(2-methoxyethyl)-3-aminopropiononitrile,N,N-bis[2-(methoxymethoxy)ethyl]-3-aminopropiononitrile, methylN-(2-cyanoethyl)-N-(2-methoxyethyl)-3-aminopropionate, methylN-(2-cyanoethyl)-N-(2-hydroxyethyl)-3-aminopropionate, methylN-(2-acetoxyethyl)-N-(2-cyanoethyl)-3-aminopropionate,N-(2-cyanoethyl)-N-ethyl-3-aminopropiononitrile,N-(2-cyanoethyl)-N-(2-hydroxyethyl)-3-aminopropiononitrile,N-(2-acetoxyethyl)-N-(2-cyanoethyl)-3-aminopropiononitrile,N-(2-cyanoethyl)-N-(2-formyloxyethyl)-3-aminopropiononitrile,N-(2-cyanoethyl)-N-(2-methoxyethyl)-3-aminopropiononitrile,N-(2-cyanoethyl)-N-[2-(methoxymethoxy)ethyl]-3-aminopropiononitrile,N-(2-cyanoethyl)-N-(3-hydroxy-1-propyl)-3-aminopropiononitrile,N-(3-acetoxy-1-propyl)-N-(2-cyanoethyl)-3-aminopropiononitrile,N-(2-cyanoethyl)-N-(3-formyloxy-1-propyl)-3-aminopropiononitrile,N-(2-cyanoethyl)-N-tetrahydrofurfuryl-3-aminopropiononitrile,N,N-bis(2-cyanoethyl)-3-aminopropiononitrile, diethylaminoacetonitrile,N,N-bis(2-hydroxyethyl)aminoacetonitrile,N,N-bis(2-acetoxyethyl)aminoacetonitrile,N,N-bis(2-formyloxyethyl)aminoacetonitrile,N,N-bis(2-methoxyethyl)aminoacetonitrile,N,N-bis[2-(methoxymethoxy)ethyl]aminoacetonitrile, methylN-cyanomethyl-N-(2-methoxyethyl)-3-aminopropionate, methylN-cyanomethyl-N-(2-hydroxyethyl)-3-aminopropionate, methylN-(2-acetoxyethyl)-N-cyanomethyl-3-aminopropionate,N-cyanomethyl-N-(2-hydroxyethyl)aminoacetonitrile,N-(2-acetoxyethyl)-N-(cyanomethyl)aminoacetonitrile,N-cyanomethyl-N-(2-formyloxyethyl)aminoacetonitrile,N-cyanomethyl-N-(2-methoxyethyl)aminoacetonitrile,N-cyanomethyl-N-[2-(methoxymethoxy)ethyl)aminoacetonitrile,N-cyanomethyl-N-(3-hydroxy-1-propyl)aminoacetonitrile,N-(3-acetoxy-1-propyl)-N-(cyanomethyl)aminoacetonitrile,N-cyanomethyl-N-(3-formyloxy-1-propyl)aminoacetonitrile,N,N-bis(cyanomethyl)aminoacetonitrile, 1-pyrrolidinepropiononitrile,1-piperidinepropiononitrile, 4-morpholinepropiononitrile,1-pyrrolidineacetonitrile, 1-piperidineacetonitrile,4-morpholineacetonitrile, cyanomethyl 3-diethylaminopropionate,cyanomethyl N,N-bis(2-hydroxyethyl)-3-aminopropionate, cyanomethylN,N-bis(2-acetoxyethyl)-3-aminopropionate, cyanomethylN,N-bis(2-formyloxyethyl)-3-aminopropionate, cyanomethylN,N-bis(2-methoxyethyl)-3-aminopropionate, cyanomethylN,N-bis[2-(methoxymethoxy)ethyl]-3-aminopropionate, 2-cyanoethyl3-diethylaminopropionate, 2-cyanoethylN,N-bis(2-hydroxyethyl)-3-aminopropionate, 2-cyanoethylN,N-bis(2-acetoxyethyl)-3-aminopropionate, 2-cyanoethylN,N-bis(2-formyloxyethyl)-3-aminopropionate, 2-cyanoethylN,N-bis(2-methoxyethyl)-3-aminopropionate, 2-cyanoethylN,N-bis[2-(methoxymethoxy)ethyl]-3-aminopropionate, cyanomethyl1-pyrrolidinepropionate, cyanomethyl 1-piperidinepropionate, cyanomethyl4-morpholinepropionate, 2-cyanoethyl 1-pyrrolidinepropionate,2-cyanoethyl 1-piperidinepropionate, and 2-cyanoethyl4-morpholinepropionate.

The basic compounds may be used alone or in admixture of two or more.The basic compound is preferably formulated in an amount of 0 to 2parts, and especially 0.01 to 1 part by weight, among 100 parts byweight of the solids in the resist composition. The use of more than 2parts of the basis compound would result in too low a sensitivity.

Component (E)

Illustrative, non-limiting, examples of the organic acid derivatives (E)include phenol, cresol, catechol, resorcinol, pyrogallol, phloroglucin,bis(4-hydroxyphenyl)methane, 2,2-bis(4′-hydroxyphenyl)propane,bis(4-hydroxyphenyl)sulfone, 1,1,1-tris(4′-hydroxyphenyl)ethane,1,1,2-tris(4′-hydroxyphenyl)ethane, hydroxybenzophenone,4-hydroxyphenylacetic acid, 3-hydroxyphenylacetic acid,2-hydroxyphenylacetic acid, 3-(4-hydroxyphenyl)propionic acid,3-(2-hydroxyphenyl)propionic acid, 2,5-dihydroxyphenylacetic acid,3,4-dihydroxyphenylacetic acid, 1,2-phenylenediacetic acid,1,3-phenylenediacetic acid, 1,4-phenylenediacetic acid,1,2-phenylenedioxydiacetic acid, 1,4-phenylenedipropanoic acid, benzoicacid, salicylic acid, 4,4-bis(4′-hydroxyphenyl)valeric acid,4-tert-butoxyphenylacetic acid, 4-(4-hydroxyphenyl)butyric acid,3,4-dihydroxymandelic acid, and 4-hydroxymandelic acid. Of these,salicylic acid and 4,4-bis(4′-hydroxyphenyl)valeric acid are preferred.They may be used alone or in admixture of two or more.

In the resist composition of the invention, the organic acid derivativeis preferably formulated in an amount of up to 5 parts, and especiallyup to 1 part by weight, among 100 parts by weight of the solids in theresist composition. The use of more than 5 parts of the organic acidderivative would result in too low a resolution. Depending on thecombination of the other components in the resist composition, theorganic acid derivative may be omitted.

Component (F)

Component (F) is an organic solvent. Illustrative, non-limiting,examples include butyl acetate, amyl acetate, cyclohexyl acetate,3-methoxybutyl acetate, methyl ethyl ketone, methyl amyl ketone,cyclohexanone, cyclopentanone, 3-ethoxyethyl propionate, 3-ethoxymethylpropionate, 3-methoxymethyl propionate, methyl acetoacetate, ethylacetoacetate, diacetone alcohol, methyl pyruvate, ethyl pyruvate,propylene glycol monomethyl ether, propylene glycol monoethyl ether,propylene glycol monomethyl ether propionate, propylene glycol monoethylether propionate, ethylene glycol monomethyl ether, ethylene glycolmonoethyl ether, diethylene glycol monomethyl ether, diethylene glycolmonoethyl ether, 3-methyl-3-methoxybutanol, N-methylpyrrolidone,dimethyl sulfoxide, γ-butyrolactone; propylene glycol alkyl etheracetates such as propylene glycol methyl ether acetate, propylene glycolethyl ether acetate, propylene glycol propyl ether acetate; alkyllactates such as methyl lactate, ethyl lactate, propyl lactate; andtetramethylene sulfone. Of these, the propylene glycol alkyl etheracetates and alkyl lactates are especially preferred. The solvents maybe used alone or in admixture of two or more. An exemplary usefulsolvent mixture is a mixture of a propylene glycol alkyl ether acetateand an alkyl lactate. It is noted that the alkyl groups of the propyleneglycol alkyl ether acetates are preferably those of 1 to 4 carbon atoms,for example, methyl, ethyl and propyl, with methyl and ethyl beingespecially preferred. Since the propylene glycol alkyl ether acetatesinclude 1,2- and 1,3-substituted ones, each includes three isomersdepending on the combination of substituted positions, which may be usedalone or in admixture. It is also noted that the alkyl groups of thealkyl lactates are preferably those of 1 to 4 carbon atoms, for example,methyl, ethyl and propyl, with methyl and ethyl being especiallypreferred.

When the propylene glycol alkyl ether acetate is used as the solvent, itpreferably accounts for at least 50% by weight of the entire solvent.Also when the alkyl lactate is used as the solvent, it preferablyaccounts for at least 50% by weight of the entire solvent. When amixture of propylene glycol alkyl ether acetate and alkyl lactate isused as the solvent, that mixture preferably accounts for at least 50%by weight of the entire solvent.

The solvent is preferably used in an amount of 300 to 2,000 parts byweight, especially 400 to 1,000 parts by weight, relative to 100 partsby weight of the solids in the resist composition. The solventconcentration is not limited thereto as long as a film can be formed byexisting methods.

Component (G)

In one preferred embodiment, the resist composition further contains (G)a compound with a molecular weight of up to 3,000 which changes itssolubility in an alkaline developer under the action of an acid, thatis, a dissolution inhibitor. Typically, a compound obtained by partiallyor entirely substituting acid labile substituents on a phenol orcarboxylic acid derivative having a molecular weight of up to 3,000,especially up to 2,500 is added as the dissolution inhibitor.

Examples of the phenol or carboxylic acid derivative having a molecularweight of up to 2,500 include bisphenol A, bisphenol H, bisphenol S,4,4-bis(4′-hydroxyphenyl)valeric acid, tris(4-hydroxyphenyl)methane,1,1,1-tris(4′-hydroxyphenyl)ethane, 1,1,2-tris(4′-hydroxyphenyl)ethane,phenolphthalein, and thymolphthalein. The acid labile substituents arethe same as those exemplified as the acid labile groups in the polymer.

Illustrative, non-limiting, examples of the dissolution inhibitors whichare useful herein include bis(4-(2′-tetrahydropyranyloxy)phenyl)methane,bis(4-(2′-tetrahydrofuranyloxy)phenyl)methane,bis(4-tert-butoxyphenyl)methane,bis(4-tert-butoxycarbonyloxyphenyl)methane,bis(4-tert-butoxycarbonylmethyloxyphenyl)methane,bis(4-(1′-ethoxyethoxy)phenyl)methane,bis(4-(1′-ethoxypropyloxy)phenyl)methane,2,2-bis(4′-(2″-tetrahydropyranyloxy))propane,2,2-bis(4′-(2″-tetrahydrofuranyloxy)phenyl)propane,2,2-bis(4′-tert-butoxyphenyl)propane,2,2-bis(4′-tert-butoxycarbonyloxyphenyl)propane,2,2-bis(4-tert-butoxycarbonylmethyloxyphenyl)propane,2,2-bis(4′-(1″-ethoxyethoxy)phenyl)propane,2,2-bis(4′-(1″-ethoxypropyloxy)phenyl)propane, tert-butyl4,4-bis(4′-(2″-tetrahydropyranyloxy)phenyl)valerate, tert-butyl4,4-bis(4′-(2″-tetrahydrofuranyloxy)phenyl)valerate, tert-butyl4,4-bis(4′-tert-butoxyphenyl)valerate, tert-butyl4,4-bis(4-tert-butoxycarbonyloxyphenyl)valerate, tert-butyl4,4-bis(4′-tert-butoxycarbonylmethyloxyphenyl)valerate, tert-butyl4,4-bis(4′-(1″-ethoxyethoxy)phenyl)valerate, tert-butyl4,4-bis(4′-(1″-ethoxypropyloxy)phenyl)valerate,tris(4-(2′-tetrahydropyranyloxy)phenyl)methane,tris(4-(2′-tetrahydrofuranyloxy)phenyl)methane,tris(4-tert-butoxyphenyl)methane,tris(4-tert-butoxycarbonyloxyphenyl)methane,tris(4-tert-butoxycarbonyloxymethylphenyl)methane,tris(4-(1′-ethoxyethoxy)phenyl)methane,tris(4-(1′-ethoxypropyloxy)phenyl)methane,1,1,2-tris(4′-(2″-tetrahydropyranyloxy)phenyl)ethane,1,1,2-tris(4′-(2″-tetrahydrofuranyloxy)phenyl)ethane,1,1,2-tris(4′-tert-butoxyphenyl)ethane,1,1,2-tris(4′-tert-butoxycarbonyloxyphenyl)ethane,1,1,2-tris(4′-tert-butoxycarbonylmethyloxyphenyl)ethane,1,1,2-tris(4′-(1′-ethoxyethoxy)phenyl)ethane, and1,1,2-tris(4′-(1′-ethoxypropyloxy)phenyl)ethane.

In the resist composition of the invention, an appropriate amount of thedissolution inhibitor is up to 20 parts, and especially up to 15 partsby weight, among 100 parts by weight of the solids in the resistcomposition. With more than 20 parts of the dissolution inhibitor, theresist composition becomes less heat resistant because of an increasedcontent of monomer components.

Component (H)

In a chemically amplified negative resist composition as well, theO-arenesulfonyloxime compound of formula (1) or (1a) according to theinvention may be used as the photoacid generator. This compositionfurther contains an alkali-soluble resin as component (H), examples ofwhich are intermediates of the above-described component (A), though notlimited thereto. Examples of the alkali-soluble resin includepoly(p-hydroxystyrene), poly(m-hydroxystyrene),poly(4-hydroxy-2-methylstyrene), poly(4-hydroxy-3-methylstyrene),poly(α-methyl-p-hydroxystyrene), partially hydrogenated p-hydroxystyrenecopolymers, p-hydroxystyrene-α-methyl-p-hydroxystyrene copolymers,p-hydroxystyrene-α-methylstyrene copolymers, p-hydroxystyrene-styrenecopolymers, p-hydroxystyrene-m-hydroxystyrene copolymers,p-hydroxystyrene-styrene copolymers, p-hydroxystyrene-acrylic acidcopolymers, p-hydroxystyrene-methacrylic acid copolymers,p-hydroxystyrene-methyl methacrylate copolymers,p-hydroxystyrene-acrylic acid-methyl methacrylate copolymers,p-hydroxystyrene-methyl acrylate copolymers,p-hydroxystyrene-methacrylic acid-methyl methacrylate copolymers,poly(methacrylic acid), poly(acrylic acid), acrylic acid-methyl acrylatecopolymers, methacrylic acid-methyl methacrylate copolymers, acrylicacid-maleimide copolymers, methacrylic acid-maleimide copolymers,p-hydroxystyrene-acrylic acid-maleimide copolymers, andp-hydroxystyrene-methacrylic acid-maleimide copolymers, but are notlimited to these combinations.

Preferred are poly(p-hydroxystyrene), partially hydrogenatedp-hydroxystyrene copolymers, p-hydroxystyrene-styrene copolymers,p-hydroxystyrene-acrylic acid copolymers, andp-hydroxystyrene-methacrylic acid copolymers.

Alkali-soluble resins comprising recurring units of the followingformula (2), (2′), (2″) or (2′″) are especially preferred.

Herein R¹ is hydrogen or methyl; and R² is a straight, branched orcyclic alkyl group of 1 to 8 carbon atoms. The subscript x is 0 or apositive integer; y is a positive integer, satisfying x+y≦5, z is 0 or apositive integer, satisfying x+z≦5; M and N are positive integers,satisfying 0<M/(M+N)≦0.5; yy is 0 or a positive integer, satisfyingx+yy≦4; A and B are positive integers, C is 0 or a positive integer,satisfying 0<B/(A+B+C)≦0.5, ZZ is a divalent organic group selected fromamong CH₂, CH(OH), CR²(OH), C═O and C(OR²)(OH), or a trivalent organicgroup represented by —C(OH)═; F is independently a positive integer, andH is a positive integer, satisfying 0.001≦H/(F+H)≦0.1; and XX is 1 or 2.

The alkali-soluble resin or polymer should preferably have a weightaverage molecular weight (Mw) of 3,000 to 100,000. Many polymers with Mwof less than 3,000 do not perform well and are poor in heat resistanceand film formation. Many polymers with Mw of more than 100,000 give riseto a problem with respect to dissolution in the resist solvent anddeveloper. The polymer should also preferably have a dispersity (Mw/Mn)of up to 3.5, and more preferably up to 1.5. With a dispersity of morethan 3.5, resolution is low in many cases. Although the preparationmethod is not critical, a poly(p-hydroxystyrene) or similar polymer witha low dispersity or narrow dispersion can be synthesized by living anionpolymerization.

To impart a certain function, suitable substituent groups may beintroduced into some of the phenolic hydroxyl and carboxyl groups on theforegoing polymer with protected acid labile groups. Exemplary andpreferred are substituent groups for improving adhesion to thesubstrate, substituent groups for improving etching resistance, andespecially substituent groups which are relatively stable against acidand alkali and effective for controlling such that the dissolution ratein an alkali developer of unexposed and low exposed areas of a resistfilm may not become too high. Illustrative, non-limiting, substituentgroups include 2-hydroxyethyl, 2-hydroxypropyl, methoxymethyl,methoxycarbonyl, ethoxycarbonyl, methoxycarbonylmethyl,ethoxycarbonylmethyl, 4-methyl-2-oxo-4-oxolanyl,4-methyl-2-oxo-4-oxanyl, methyl, ethyl, n-propyl, isopropyl, n-butyl,sec-butyl, acetyl, pivaloyl, adamantyl, isoboronyl, and cyclohexyl. Itis also possible to introduce acid-decomposable substituent groups suchas t-butoxycarbonyl and relatively acid-undecomposable substituentgroups such as t-butyl and t-butoxycarbonylmethyl.

In the resist composition, the above resin (H) is blended in any desiredamount, preferably of 65 to 99 parts by weight, especially 65 to 98parts by weight among 100 parts by weight of the solids.

Component (I)

Also contained in the negative resist composition is (I) an acidcrosslinker capable of forming a crosslinked structure under the actionof an acid. Typical acid crosslinkers are compounds having at least twohydroxymethyl, alkoxymethyl, epoxy or vinyl ether groups in a molecule.Substituted glycoluril derivatives, urea derivatives, andhexa(methoxymethyl)melamine compounds are suitable as the acidcrosslinker in the chemically amplified, negative resist composition.Examples include N,N,N′,N′-tetramethoxymethylurea,hexamethoxymethylmelamine, tetraalkoxymethyl-substituted glycolurilcompounds such as tetrahydroxymethyl-substituted glycoluril andtetramethoxymethylglycoluril, and condensates of phenolic compounds suchas substituted or unsubstituted bis(hydroxymethylphenol) compounds andbisphenol A with epichlorohydrin. Especially preferred acid crosslinkersinclude 1,3,5,7-tetraalkoxymethylglycolurils such as1,3,5,7-tetramethoxymethylglycoluril, as well as1,3,5,7-tetrahydroxymethylglycoluril, 2,6-dihydroxymethyl-p-cresol,2,6-dihydroxymethylphenol, 2,2′,6,6′-tetrahydroxymethyl-bisphenol A,1,4-bis[2-(2-hydroxypropyl)]benzene, N,N,N′,N′-tetramethoxymethylurea,and hexamethoxymethylmelamine.

An appropriate amount of the acid crosslinker is, but not limitedthereto, about 1 to 20 parts, and especially about 5 to 15 parts byweight among 100 parts by weight of the solids in the resistcomposition. The acid crosslinkers may be used alone or in admixture ofany.

Component (J)

Component (J) is an alkali-soluble compound having a molecular weight ofup to 2,500. Any suitable compound may be used although a compoundhaving at least two phenol and/or carboxyl groups is preferred.Illustrative, non-limiting, examples of the alkali-soluble compound (J)include cresol, catechol, resorcinol, pyrogallol, phloroglucin,bis(4-hydroxyphenyl)methane, 2,2-bis(4′-hydroxyphenyl)propane,bis(4-hydroxyphenyl)sulfone, 1,1,1-tris(4′-hydroxyphenyl)ethane,1,1,2-tris(4′-hydroxyphenyl)ethane, hydroxybenzophenone,4-hydroxyphenylacetic acid, 3-hydroxyphenylacetic acid,2-hydroxyphenylacetic acid, 3-(4-hydroxyphenyl)propionic acid,3-(2-hydroxyphenyl)propionic acid, 2,5-dihydroxyphenylacetic acid,3,4-dihydroxyphenylacetic acid, 1,2-phenylenediacetic acid,1,3-phenylenediacetic acid, 1,4-phenylenediacetic acid,1,2-phenylenedioxydiacetic acid, 1,4-phenylenedipropanoic acid, benzoicacid, salicylic acid, 4,4-bis(4′-hydroxyphenyl)valeric acid,4-tert-butoxyphenylacetic acid, 4-(4-hydroxyphenyl)butyric acid,3,4-dihydroxymandelic acid, and 4-hydroxymandelic acid. Of these,salicylic acid and 4,4-bis(4′-hydroxyphenyl)valeric acid are preferred.They may be used alone or in admixture of two or more. Thealkali-soluble compound is blended in any desired amount, preferably of0 to 20 parts by weight, especially 2 to 10 parts by weight among 100parts by weight of the solids in the resist composition.

In the chemically amplified resist composition of the invention, theremay be added such additives as surfactants for improving coating, lightabsorbing agents (typically, UV absorbers) for reducing diffusereflection from the substrate, and thermal flow regulators.

Illustrative, non-limiting, examples of the surfactant include nonionicsurfactants, for example, polyoxyethylene alkyl ethers such aspolyoxyethylene lauryl ether, polyoxyethylene stearyl ether,polyoxyethylene cetyl ether, and polyoxyethylene oleyl ether,polyoxyethylene alkylaryl ethers such as polyoxyethylene octylphenolether and polyoxyethylene nonylphenol ether, polyoxyethylenepolyoxypropylene block copolymers, sorbitan fatty acid esters such assorbitan monolaurate, sorbitan monopalmitate, and sorbitan monostearate,and polyoxyethylene sorbitan fatty acid esters such as polyoxyethylenesorbitan monolaurate, polyoxyethylene sorbitan monopalmitate,polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitantrioleate, and polyoxyethylene sorbitan tristearate; fluorochemicalsurfactants such as EFTOP EF301, EF303 and EF352 (Tohkem Products Co.,Ltd.), Megaface F171, F172 and F173 (Dai-Nippon Ink & Chemicals, Inc.),Fluorad FC430 and FC431 (Sumitomo 3M Co., Ltd.), Aashiguard AG710,Surflon S-381, S-382, SC101, SC102, SC103, SC104, SC105, SC106, SurfynolE1004, KH-10, KH-20, KH-30 and KH-40 (Asahi Glass Co., Ltd.);organosiloxane polymers KP341, X-70-092 and X-70-093 (Shin-Etsu ChemicalCo., Ltd.), acrylic acid or methacrylic acid Polyflow No. 75 and No. 95(Kyoeisha Ushi Kagaku Kogyo Co., Ltd.). Inter alia, FC430, SurflonS-381, Surfynol E1004, KH-20 and KH-30 are preferred. These surfactantsmay be used alone or in admixture.

In the chemically amplified resist composition according to theinvention, the surfactant is preferably formulated in an amount of up to2 parts, and especially up to 1 part by weight, among 100 parts byweight of the solids in the resist composition.

In the chemically amplified resist composition according to theinvention, UV absorbers may be added. Those UV absorbers described inJP-A 11-190904 are useful, but the invention is not limited thereto.Exemplary UV absorbers are diaryl sulfoxide derivatives such asbis(4-hydroxyphenyl)sulfoxide, bis(4-tert-butoxyphenyl)sulfoxide,bis(4-tert-butoxycarbonyloxyphenyl)sulfoxide, andbis[4-(1-ethoxyethoxy)phenyl]sulfoxide; diarylsulfone derivatives suchas bis(4-hydroxyphenyl)sulfone, bis(4-tert-butoxyphenyl)sulfone,bis(4-tert-butoxycarbonyloxyphenyl)sulfone,bis[4-(1-ethoxyethoxy)phenyl]sulfone, andbis[4-(1-ethoxypropoxy)phenyl]sulfone; diazo compounds such asbenzoquinonediazide, naphthoquinonediazide, anthraquinonediazide,diazofluorene, diazotetralone, and diazophenanthrone; quinonediazidegroup-containing compounds such as complete or partial ester compoundsbetween naphthoquinone-1,2-diazide-5-sulfonic acid chloride and2,3,4-trihydroxybenzophenone and complete or partial ester compoundsbetween naphthoquinone-1,2-diazide-4-sulfonic acid chloride and2,4,4′-trihydroxybenzophenone; tert-butyl 9-anthracenecarboxylate,tert-amyl 9-anthracenecarboxylate, tert-methoxymethyl9-anthracenecarboxylate, tert-ethoxyethyl 9-anthracenecarboxylate,2-tert-tetrahydropyranyl 9-anthracenecarboxylate, and2-tert-tetrahydrofuranyl 9-anthracenecarboxylate. The UV absorber may ormay not be added to the resist composition depending on the type ofresist composition. An appropriate amount of UV absorber, if added, is 0to 10 parts, more preferably 0.5 to 10 parts, most preferably 1 to 5parts by weight, among 100 parts by weight of the base resin.

Suitable thermal flow regulators are organic compounds which do notreact with any components in the resist composition or alter theresolution capability thereof, and preferably aliphatic compounds havingpH 5.0 to 8.0 and a boiling point of at least 200° C. under atmosphericpressure. Preferred examples include, but are not limited to,polyoxyalkylene alkyl ether esters, polyoxyalkylene alkyl ethers,polyoxyalkylene dialkyl ethers, polyoxyalkylene aralkyl alkyl ethers,polyoxyalkylene aralkyl ethers, polyoxyalkylene diaralkyl ethers, andpolyoxyalkylene laurates. Also useful are polyoxyethylene nonyl phenylether, polyoxyethylene alkyl ethers, polyoxyethylene lauryl ether,polyoxyethylene higher alcohol ethers, polyoxyalkylene alkyl ethers,polyoxyethylene derivatives, and polyoxyethylene sorbitan monolaurate.These compounds may be used alone or in admixture of two or more.Commercially available thermal flow regulators include Sunmol N-60SM(polyoxyethylene nonyl phenyl ether), L-50 (polyoxyethylene alkylether), and SE-70 (polyoxyethylene alkyl ether), available from NiccaChemical Co., Ltd.; and Emulgen 108 (polyoxyethylene lauryl ether), 707(polyoxyethylene higher alcohol ether), 709 (polyoxyethylene higheralcohol ether), LS-106 (polyoxyalkylene alkyl ether), LS-110(polyoxyalkylene alkyl ether), MS-110 (polyoxyalkylene alkyl ether),A-60 (polyoxyethylene derivative), B-66 (polyoxyethylene derivative),and Rheodol TW-L106 (polyoxyethylene sorbitan monolaurate), allavailable from Kao Corp. Inter alia, Emulgen MS-110 and Rheodol TW-L106are preferred.

An appropriate flow quantity may be achieved by regulating the amount ofthe above organic compound added to the resist composition, preferablyin a range of 0.2 to 5% by weight, more preferably 0.5 to 2% by weightbased on the weight of the base resin. For more detail, reference shouldbe made to JP-A 2004-333779.

For the microfabrication of integrated circuits, any well-knownlithography may be used to form a resist pattern from the chemicallyamplified resist composition comprising the photoacid generator offormula (1) or (1a) according to the invention.

The composition is applied onto a substrate (e.g., Si, SiO₂, SiN, SiON,TiN, WSi, BPSG, SOG, organic anti-reflecting film, etc.) formicrofabrication by a suitable coating technique such as spin coating,roll coating, flow coating, dip coating, spray coating or doctorcoating. The coating is prebaked on a hot plate at a temperature of 60to 150° C. for about 1 to 10 minutes, preferably 80 to 120° C. for 1 to5 minutes. The resulting resist film is generally 0.1 to 2.0 μm thick.Through a photomask having a desired pattern, the resist film is thenexposed to radiation, preferably having an exposure wavelength of up to300 nm, such as UV, deep-UV, electron beams, x-rays, excimer laserlight, γ-rays and synchrotron radiation. The preferred light source is abeam from an excimer laser, especially KrF excimer laser or deep UV of245-255 nm wavelength. The exposure dose is preferably in the range ofabout 1 to 200 mJ/cm², more preferably about 10 to 100 mJ/cm². The filmis post-exposure baked (PEB) on a hot plate at 60 to 150° C. for 1 to 5minutes, preferably 80 to 120° C. for 1 to 3 minutes.

Thereafter the resist film is developed with a developer in the form ofan aqueous base solution, for example, 0.1 to 5%, preferably 2 to 3%aqueous solution of tetramethylammonium hydroxide (TMAH) for 0.1 to 3minutes, preferably 0.5 to 2 minutes by conventional techniques such asdip, puddle or spray development. In this way, a desired resist patternis formed on the substrate. It is appreciated that the resistcomposition of the invention is best suited for micro-patterning usingsuch actinic radiation as deep UV with a wavelength of 254 to 193 nm,vacuum UV with a wavelength of 157 nm, electron beams, x-rays, excimerlaser light, γ-rays and synchrotron radiation. With any of theabove-described parameters outside the above-described range, theprocess may sometimes fail to produce the desired pattern.

Where a thermal flow step is involved, a resist pattern, especially acontact hole pattern which has been formed as mentioned above is heatedon a hot plate. The heating temperature for thermal flow is preferablyin a range of 100 to 200° C., and more preferably 100 to 150° C. withthe precision of the hot plate being taken into account. The heattreatment time is preferably 60 to 120 seconds. While the contact holepattern formed by exposure and development generally has a size of 0.20to 0.30 μm, the thermal flow reduces the contact hole size, enablingformation of a ultrafine contact hole pattern with a size of 0.10 to0.15 μM.

EXAMPLE

Examples of the invention are given below by way of illustration and notby way of limitation. Mw is weight average molecular weight.

Synthesis Example 1 Synthesis of sodium4-(4′-methylphenylsulfonyloxy)benzenesulfonate

In 400 g of tetrahydrofuran and 250 g of water were dissolved 208 g (1.0mol) of 4-phenolsulfonic acid hydrate and 191 g (1.0 mol) ofp-toluenesulfonic acid chloride. With ice cooling and stirring, anaqueous sodium hydroxide solution (80 g (2.0 mol) of sodium hydroxide in125 g of water) was added dropwise such that the temperature might notexceed 20° C. After the completion of dropwise addition, the solutionwas allowed to ripen for 2 hours at room temperature. To the reactionsolution, 700 g of dichloromethane was added to help sodium4-(4′-methylphenylsulfonyloxy)benzenesulfonate crystallize. The crystalswere collected by filtration, washed with 200 g of dichloromethane, anddried in vacuum at 60° C. for 12 hours. The amount was 330 g (yield94%).

Synthesis Example 2 Synthesis of sodium2,5-bis(4′-methylphenylsulfonyloxy)benzenesulfonate

By substantially following Synthesis Example 1 except that 1.0 mol ofpotassium hydroquinonesulfonate was used instead of the 4-phenolsulfonicacid hydrate and 2.5 mol of p-toluenesulfonic acid chloride was used,the target compound, sodium2,5-bis(4′-methylphenylsulfonyloxy)benzenesulfonate was synthesized.

Synthesis Example 3 Synthesis of sodium6-(4′-methylphenylsulfonyloxy)naphthalene-2-sulfonate

In 100 g of tetrahydrofuran and 80 g of water were dissolved 50 g (0.18mol) of sodium 2,6-naphtholsulfonate hydrate and 33.8 g (0.18 mol) ofp-toluenesulfonic acid chloride. With ice cooling and stirring, anaqueous sodium hydroxide solution (7.1 g (0.18 mol) of sodium hydroxidein 30 g of water) was added dropwise such that the temperature might notexceed 20° C. After the completion of dropwise addition, the solutionwas allowed to ripen for 2 hours at room temperature. To the reactionsolution, 600 g of dichloromethane was added to help sodium6-(4′-methylphenylsulfonyloxy)naphthalene-2-sulfonate crystallize. Thecrystals were collected by filtration, washed with 300 g ofdichloromethane, and dried in vacuum at 60° C. for 12 hours. The amountwas 62 g (yield 86%).

Synthesis Example 4 Synthesis of sodium4-(4′-methylphenylsulfonyloxy)naphthalene-1-sulfonate

In 59 g of tetrahydrofuran and 23 g of water were dissolved 25 g (0.09mol) of sodium 1,4-naphtholsulfonate hydrate and 16.8 g (0.09 mol) ofp-toluenesulfonic acid chloride. With ice cooling and stirring, anaqueous sodium hydroxide solution (3.5 g (0.09 mol) of sodium hydroxidein 27 g of water) was added dropwise such that the temperature might notexceed 20° C. After the completion of dropwise addition, the solutionwas allowed to ripen for 2 hours at room temperature. To the reactionsolution, 700 g of dichloromethane was added to help sodium4-(4′-methylphenylsulfonyloxy)naphthalene-1-sulfonate crystallize. Thecrystals were collected by filtration, washed with 300 g ofdichloromethane, and dried in vacuum at 60° C. for 12 hours. The amountwas 30 g (yield 83%).

Synthesis Example 5 Synthesis of sodium8-(4′-methylphenylsulfonyloxy)naphthalene-1-sulfonate

In 24 g of tetrahydrofuran and 11 g of water were dissolved 12.3 g (0.05mol) of sodium 1,8-naphtholsulfonate hydrate and 9.5 g (0.05 mol) ofp-toluenesulfonic acid chloride. With ice cooling and stirring, anaqueous sodium hydroxide solution (2 g (0.05 mol) of sodium hydroxide in9 g of water) was added dropwise such that the temperature might notexceed 20° C. After the completion of dropwise addition, the solutionwas allowed to ripen for 2 hours at room temperature. To the reactionsolution, 100 g of dichloromethane was added to help sodium8-(4′-methylphenylsulfonyloxy)naphthalene-1-sulfonate crystallize. Thecrystals were collected by filtration, washed with 300 g ofdichloromethane, and dried in vacuum at 60° C. for 12 hours. The amountwas 17 g (yield 85%).

Synthesis Example 6 Synthesis of sodium3-methoxy-4-(4′-methylphenylsulfonyloxy)benzenesulfonate

In 80 g of tetrahydrofuran and 65 g of water were dissolved 50 g (0.2mol) of potassium guaiacolsulfonate hydrate and 38 g (0.2 mol) ofp-toluenesulfonic acid chloride. With ice cooling and stirring, anaqueous sodium hydroxide solution (8 g (0.2 mol) of sodium hydroxide in15 g of water) was added dropwise such that the temperature might notexceed 20° C. After the completion of dropwise addition, the solutionwas allowed to ripen for 2 hours at room temperature. To the reactionsolution, 200 g of dichloromethane was added to help sodium3-methoxy-4-(4′-methylphenylsulfonyloxy)benzenesulfonate crystallize.The crystals were collected by filtration, washed with 200 g ofdichloromethane, and dried in vacuum at 60° C. for 12 hours. The amountwas 72 g (yield 94% as Na salt).

It is noted that the crystalline product thus obtained could be amixture of sodium and potassium salts. The product was directly used inthe subsequent step of halogenation reaction without purificationbecause the metals can be removed as sodium and potassium ions in thehalogenation reaction.

Synthesis Example 7 Synthesis of4-(4′-methylphenylsulfonyloxy)benzenesulfonyl chloride

In 80 g of carbon tetrachloride, 20 g (0.057 mol) of sodium4-(4′-methylphenylsulfonyloxy)benzenesulfonate, obtained in SynthesisExample 1, was dispersed by stirring under ice cooling. To thesuspension, 23.8 g (0.114 mol) of phosphorus pentachloride was slowlyadded such that the temperature might not exceed 20° C. The suspensionwas stirred for one hour under ice cooling and then for 12 hours at roomtemperature. After the ripening, the reaction solution was poured into150 g of ice water whereupon a white oily matter separated out. The oilymatter was extracted with 100 g of dichloromethane, dried over anhydrousmagnesium sulfate, and filtered. The solvent was distilled off invacuum, yielding 15.9 g of white crystals (yield 81%).

Synthesis Examples 8-12

The procedure of Synthesis Example 7 was repeated aside from using thearylsulfonyloxyarylsulfonic acid salts of Synthesis Examples 2 to 6instead of the sodium 4-(4′-methylphenylsulfonyloxy)benzenesulfonateused in Synthesis Example 7. The corresponding sulfonyl chlorides wereaccordingly synthesized.

Synthesis Example 8 2,5-bis(4′-methylphenylsulfonyloxy)benzenesulfonylchloride Synthesis Example 96-(4′-methylphenylsulfonyloxy)naphthalene-2-sulfonyl chloride SynthesisExample 10 4-(4′-methylphenylsulfonyloxy)naphthalene-1-sulfonyl chlorideSynthesis Example 118-(4′-methylphenylsulfonyloxy)naphthalene-1-sulfonyl chloride SynthesisExample 12 3-methoxy-4-(4′-methylphenylsulfonyloxy)benzenesulfonylchloride Synthesis Example 13

Synthesis was carried out as in Synthesis Example 7 aside from usingO-cresolsulfonic acid instead of the 4-phenolsulfonic acid hydrate inSynthesis Example 1, yielding3-methyl-4-(4′-methylphenylsulfonyloxy)benzenesulfonyl chloride.

Synthesis Example 14 Synthesis of(3-(hydroxy)imino-3H-thiophen-2-ylidene)-(2-methylphenyl)-acetonitrile

A solution of 128 g (2.3 mol) of potassium hydroxide in 364 g ofmethanol was cooled, to which 75 g (0.57 mol) of o-xylyl cyanide wasadded. Thereafter, a solution of 75 g (0.58 mol) of 2-nitrothiophene(purity 85%) in 218 g of methanol was added dropwise such that thetemperature might not exceed 5° C. The solution was allowed to ripen for30 minutes below 5° C., after which a solution of 551 g of glacialacetic acid in 2,200 g of water was added, and further 1,000 g of ethylacetate added. The organic layer was separated. Ethyl acetate, 400 g,was added to the aqueous layer to effect extraction again. The organiclayers were combined, washed with 200 g of saturated sodium chloridewater two times, dried over anhydrous magnesium sulfate, andconcentrated in vacuum, obtaining 125 g of an oily matter. It waspurified by silica gel column chromatography (eluent, ethylacetate:hexane=2:1 by volume). The elute was concentrated, followed byrecrystallization from toluene, filtration and drying. There wasobtained 49 g of yellow crystals (yield 35%).

The compound was analyzed by nuclear magnetic resonance (NMR)spectroscopy and infrared (IR) absorption spectroscopy, with the datashown below.

¹H-NMR: CDCl₃ (ppm) 2.37 (3H, s, Ha) 6.09-6.11 (1H, d, Hf) 6.88-6.90(1H, d, Hg) 7.20-7.36 (4H, m, Hb, Hc, Hd, He) 9.23 (1H, s, Hh)

IR: cm⁻¹ 3253, 3075, 3016, 2958, 2825, 2208, 1540, 1521, 1483, 1456,1423, 1386, 1330, 1290, 1257, 1232, 1101, 1068, 1012, 991, 844, 798,763, 734, 723, 692, 678, 644

Synthesis Example 15 Synthesis of(3-(4-(4-methylphenylsulfonyloxy)phenylsulfonyloxy)imino-3H-thiophen-2-ylidene)-(2-methylphenyl)-acetonitrile

In 490 g of tetrahydrofuran were dissolved 45 g (0.19 mol) of(3-(hydroxy)imino-3H-thiophen-2-ylidene)-(2-methylphenyl)-acetonitrilein Synthesis Example 14 and 61.8 g (0.19 mol) of4-(4′-methylphenylsulfonyloxy)benzenesulfonyl chloride in SynthesisExample 7. To the solution cooled, 20.6 g (0.20 mol) of triethylaminewas added dropwise such that the temperature might not exceed 10° C. Thesolution was allowed to ripen for 1 hour at room temperature, afterwhich 150 g of water and 500 g of dichloromethane were added. Theorganic layer was separated, and washed with 150 g of water three times.The organic layer was concentrated in vacuum to 130 g. Methanol wasadded to the concentrate for recrystallization, followed by filtrationand drying. There was obtained 83 g of yellow crystals. The crystalswere purified by silica gel column chromatography (eluent,dichloromethane). The elute was concentrated, followed byrecrystallization from methanol, filtration and drying. There wasobtained 77 g of yellow crystals (yield 72%).

The compound was analyzed by NMR and IR spectroscopy, with the datashown below.

¹H-NMR: CDCl₃ (ppm) 2.32 (3H, s, Ha) 2.46 (3H, s, Hl) 6.09-6.11 (1H, d,Hg or Hf) 6.78-6.80 (1H, d, Hf or Hg) 7.15-7.38 (8H, m, Hi, Hk, Hb, Hc,Hd, He) 7.71-7.73 (2H, d, Hj) 8.15-8.18 (2H, d, Hh)

IR: cm⁻¹ 2202, 1733, 1587, 1525, 1487, 1456, 1405, 1383, 1296, 1261,1236, 1195, 1178, 1157, 1120, 1092, 1041, 1016, 852, 816, 793, 754, 731,706, 677, 650, 625, 609, 586, 563, 549, 444

Synthesis Examples 16-21

The target compounds shown below were synthesized by the same proceduresas in Synthesis Examples 14 and 15 except that the sulfonyl chlorides ofSynthesis Examples 8 to 13 were used instead of the4-(4′-methylphenylsulfonyloxy)benzenesulfonyl chloride in SynthesisExample 15.

Synthesis Example 16(3-(2,5-bis(4-methylphenylsulfonyloxy)benzenesulfonyloxy)imino-3H-thiophen-2-ylidene)-(2-methylphenyl)-acetonitrileSynthesis Example 17(3-(6-(4-methylphenylsulfonyloxy)naphthalene-2-sulfonyloxy)imino-3H-thiophen-2-ylidene)-(2-methylphenyl)-acetonitrileSynthesis Example 18(3-(4-(4-methylphenylsulfonyloxy)naphthalene-1-sulfonyloxy)imino-3H-thiophen-2-ylidene)-(2-methylphenyl)-acetonitrileSynthesis Example 19(3-(8-(4-methylphenylsulfonyloxy)naphthalene-1-sulfonyloxy)imino-3H-thiophen-2-ylidene)-(2-methylphenyl)-acetonitrileSynthesis Example 20(3-(3-methoxy-4-(4-methylphenylsulfonyloxy)benzenesulfonyloxy)imino-3H-thiophen-2-ylidene)-(2-methylphenyl)-acetonitrileSynthesis Example 21(3-(3-methyl-4-(4-methylphenylsulfonyloxy)benzenesulfonyloxy)imino-3H-thiophen-2-ylidene)-(2-methylphenyl)-acetonitrileExamples 1-9 and Comparative Examples 1-3

Resist materials were prepared in accordance with the formulation shownin Table 1. The components used are shown below.

-   Polymer A: p-hydroxystyrene/p-1,1-dimethylethoxy-styrene copolymer    having a compositional ratio (molar ratio) of 70:30 and a Mw of    10,000-   Polymer B: p-hydroxystyrene/p-1,1-dimethylpropoxy-styrene copolymer    having a compositional ratio (molar ratio) of 70:30 and a Mw of    10,000-   Polymer C:    p-hydroxystyrene/p-1,1-dimethylethoxy-styrene/2-ethyl-2-adamantyl    acrylate copolymer having a compositional ratio (molar ratio) of    70:20:10 and a Mw of 15,000-   Polymer D:    p-hydroxystyrene/p-1,1-dimethylpropoxy-styrene/1-ethyl-1-norbornene    methacrylate copolymer having a compositional ratio (molar ratio) of    75:20:5 and a Mw of 15,000-   Polymer E: p-hydroxystyrene/p-1,1-dimethylpropoxy-styrene/tert-butyl    acrylate copolymer having a compositional ratio (molar ratio) of    70:25:5 and a Mw of 15,000-   Polymer F:    p-hydroxystyrene/p-1,1-dimethylpropoxy-styrene/1-ethylcyclopentyl    methacrylate copolymer having a compositional ratio (molar ratio) of    75:20:5 and a Mw of 15,000-   Polymer G:    p-hydroxystyrene/p-1,1-dimethylpropoxy-styrene/1-ethylcyclopentyl    methacrylate/indene copolymer having a compositional ratio (molar    ratio) of 75:10:8:7 and a Mw of 12,000-   Polymer H: poly(p-hydroxystyrene) in which hydroxyl groups are    protected with 30 mol % of 1-ethoxyethyl groups, having a Mw of    12,000-   PAG1: compound of Synthesis Example 15-   PAG2: compound of Synthesis Example 16-   PAG3: compound of Synthesis Example 17-   PAG4: triphenylsulfonium nonafluoro-1-butane-sulfonate-   PAG5: (4-tert-butoxyphenyl)diphenylsulfonium 10-camphorsulfonate-   PAG6: triphenylsulfonium 4-(4-toluenesulfonyl)-oxybenzenesulfonate-   PAG7: bis(cyclohexylsulfonyl)diazomethane-   PAG8:    (5-(10-camphorsulfonyloxy)imino-5H-thiophen-2-ylidene)-(2-methylphenyl)-acetonitrile-   PAG9:    (5-(4-toluenesulfonyloxy)imino-5H-thiphen-2-ylidene)-(2-methylphenyl)-acetonitrile-   Basic compound A: tri-n-butylamine-   Basic compound B: tris(2-methoxyethyl)amine-   Organic acid derivative A: 4,4-bis(4′-hydroxyphenyl)valeric acid-   Thermal flow regulator: Emulgen MS-110 (Kao Corp.)-   Surfactant A: FC-430 (Sumitomo 3M Co., Ltd.)-   Surfactant B: Surflon S-381 (Asahi Glass Co., Ltd.)-   Organic solvent A: propylene glycol methyl ether acetate-   Organic solvent B: ethyl lactate

TABLE 1 Comparative Example Example Composition (pbw) 1 2 3 4 5 6 7 8 91 2 3 Polymer A 80 40 80 40 Polymer B 80 40 Polymer C 80 40 Polymer D 80Polymer E 80 Polymer F 80 Polymer G 80 40 Polymer H 40 80 PAG1 1 1 1 1 10.5 1 1 PAG2 1 PAG3 0.5 PAG4 1 1 1 1 PAG5 1 1 1 1 1 1 2 PAG6 1 2 1 1PAG7 2 1 2 1 1 2 4 2 2 PAG8 0.5 PAG9 1 1 Basic compound A 0.3 0.3 0.30.3 0.3 0.3 0.15 0.3 0.3 Basic compound B 0.3 0.3 0.3 0.15 Thermal flow1 1 1 1 regulator Organic acid 0.5 0.5 derivative A Surfactant A 0.250.25 0.25 0.25 0.25 0.25 Surfactant B 0.25 0.25 0.25 0.25 0.25 0.25Solvent A 385 385 385 280 385 385 385 385 385 280 382 385 Solvent B 105105

The resist materials thus obtained were each filtered through a 0.2-μmTeflon® filter, thereby giving resist solutions. These resist solutionswere spin-coated onto 8-inch silicon wafers having an organicantireflection film (Brewer Science, DUV-44) of 610 Å thick coatedthereon, so as to give a dry thickness of 0.4 μm. For the coating andsubsequent baking and developing steps, a coater/developer Clean TrackAct 8 by Tokyo Electron Ltd. was used.

The coated wafer was then baked on a hot plate at 110° C. for 90seconds. The resist films were exposed to ⅔ annular illumination usingan excimer laser scanner NSR-S203B (Nikon Corp., NA 0.68), then baked(PEB) at 110° C. for 90 seconds, and developed with a solution of 2.38%tetramethylammonium hydroxide in water, thereby giving positive patterns(Examples 1-9 and Comparative Examples 1-3).

The resulting resist patterns were evaluated as described below.

Resist Pattern Evaluation

The optimum exposure dose (sensitivity Eop) was the exposure dose whichprovided a 1:1 resolution at the top and bottom of a 0.16-μm denselypacked contact hole pattern. The minimum hole size (μm) of a contacthole pattern which was ascertained separate at this dose was theresolution of a test resist. The shape in cross section of the resolvedresist pattern was examined under a scanning electron microscope (SEM).The depth of focus (DOF) was determined by offsetting the focal pointand judging the resist to be satisfactory when the resist pattern shapewas kept rectangular and the resist pattern film thickness was keptabove 80% of that at accurate focusing.

A top loss resulting from a resist top portion being dissolved away wasdetermined by observing the 0.16-μm dense contact hole pattern under atop-down SEM and inspecting a white ring in the periphery of a hole(observable as a film thickness change in the periphery of a hole). Asample with no white ring observed is judged acceptable (OK) and asample with white rings observed is unacceptable (NG).

The resolution of a resist was also determined with respect to a 0.20-μmisolated (1:5) hole pattern. The 0.20-μm isolated (1:5) hole pattern wasproduced while exposing at the optimum dose for resolution of the0.16-μm dense contact hole pattern and shifting the focal depth by −0.2μm. The shape in cross section of the resolved resist pattern wasexamined under a SEM. A pattern which has been resolved to the bottom ofholes is judged acceptable (OK).

The PED stability of a resist was evaluated with respect to a 0.16-μmdense contact hole pattern by effecting post-exposure bake (PEB) after24 hours of holding from exposure at the optimum dose and determining avariation of 0.16-μm hole size. A less variation value indicates greaterPED stability.

For examining the level of standing waves, a resist pattern wassimilarly produced except that the resist solution was spin coated ontoa 8-inch silicon wafer (bare silicon) to a thickness of 0.4 μm. Theoptimum exposure dose (sensitivity Eop) was the exposure dose whichprovided a 1:1 resolution at the top and bottom of a 0.18-μm densecontact hole pattern (differring from the optimum dose for 0.16 μm). Theshape in cross section of the resist pattern resolved at this optimumdose was observed under a SEM and visually determined. A sample with nostanding waves observable is judged acceptable (OK) while a sample withstanding waves observable is unacceptable (NG).

The results of resist pattern evaluation are shown in Table 2.

TABLE 2 0.16-μm Resolution 24-hr PED pattern Resist of dimensionalSensitivity Resolution Profile DOF top isolated stability Standing(mJ/cm²) (μm) shape (μm) shape pattern (nm) waves Example 1 70 0.15rectangular 1.0 OK OK 0 OK Example 2 75 0.15 rectangular 1.0 OK OK 0 OKExample 3 73 0.15 rectangular 0.8 OK OK 0 OK Example 4 73 0.15rectangular 0.8 OK OK 0 OK Example 5 70 0.15 rectangular 1.0 OK OK 0 OKExample 6 75 0.15 rectangular 1.0 OK OK 0 OK Example 7 73 0.15rectangular 0.8 OK OK 0 OK Example 8 73 0.15 rectangular 0.8 OK OK 0 OKExample 9 70 0.15 rectangular 0.8 OK OK 0 OK Comparative 75 0.15rectangular 0.8 OK NG 0 OK Example 1 Comparative 70 0.15 rounded top 0.8NG NG 4 NG Example 2 Comparative 73 0.15 rounded top 0.8 NG OK 10 NGExample 3Other Evaluation

The solubility of resist material in a solvent mixture was examined byvisual observation and in terms of clogging upon filtration.

With respect to the applicability of a resist solution, uneven coatingwas visually observed. Additionally, using a thickness gage Lambda AceVM-3010 (optical interference thickness gage by Dainippon Screen Mfg.Co., Ltd.), the thickness of a resist film on a common wafer wasmeasured at different positions, based on which a variation from thedesired coating thickness (0.6 μm) was calculated. The applicability wasrated “good” when the variation was within 0.5% (that is, within 0.003μm), “fair” when the variation was from more than 0.5% to 1%, and “poor”when the variation was more than 1%.

Storage stability was judged in terms of foreign matter precipitation orsensitivity change with the passage of time. After the resist solutionwas aged for 100 days at the longest, the number of particles of greaterthan 0.3 μm per ml of the resist solution was counted by means of aparticle counter KL-20A (Rion Co., Ltd.), and the foreign matterprecipitation was determined “good” when the number of particles is notmore than 5. Also, the sensitivity change was rated “good” when a changewith time of sensitivity (Eop) was within 5% from that immediately afterpreparation. Samples outside the ranges are rated “poor”.

The results are shown in Table 3.

TABLE 3 Storage Solubility Applicability stability Example 1 good goodgood Example 2 good good good Example 3 good good good Example 4 goodgood good Example 5 good good good Example 6 good good good Example 7good good good Example 8 good good good Example 9 good good goodComparative Example 1 good good good Comparative Example 2 good goodgood Comparative Example 3 good good good

Further, the compositions of Examples 1, 2 and 6 and Comparative Example1 were examined for thermal flow by the following procedure. The resultsare shown in Table 4.

Thermal Flow Test

The optimum exposure dose (sensitivity Eop) was the exposure dose whichprovided a 1:1 resolution at the top and bottom of a 0.16-μm densecontact hole pattern. The contact hole pattern which was ascertainedseparate at this dose was heated on a hot plate at 150° C. for 100seconds to cause the resist to flow for reducing the hole pattern to asize of 0.10 μm. A sample wherein a hole pattern size variation in thewafer plane falls within ±10% is judged good while a sample with a holepattern size variation in excess of ±10% is poor.

TABLE 4 Thermal flow Example 1 good Example 2 good Example 6 goodComparative Example 1 poor

Japanese Patent Application No. 2006-160575 is incorporated herein byreference.

Although some preferred embodiments have been described, manymodifications and variations may be made thereto in light of the aboveteachings. It is therefore to be understood that the invention may bepracticed otherwise than as specifically described without departingfrom the scope of the appended claims.

1. A photoacid generator for use in chemically amplified resistcompositions, having the general formula (1):

wherein R is independently selected from the class consisting ofhydrogen, fluorine, chlorine atoms, nitro groups, and substituted orunsubstituted, straight, branched or cyclic alkyl and alkoxy groups of 1to 12 carbon atoms, n is 0 or 1, m is 1 or 2, r is an integer of 0 to 4,and r′ is an integer of 0 to
 5. 2. A photoacid generator for use inchemically amplified resist compositions, having the formula (1a):


3. A chemically amplified resist composition comprising (A) a resinwhich changes its solubility in an alkaline developer under the actionof an acid, and (B) the photoacid generator of claim
 1. 4. A chemicallyamplified positive resist composition comprising (A) a resin whichchanges its solubility in an alkaline developer under the action of anacid, and (B) the photoacid generator of claim
 1. 5. The resistcomposition of claim 3, further comprising (C) a compound capable ofgenerating an acid upon exposure to radiation, other than component (B).6. The resist composition of claim 3 wherein the resin (A) has suchsubstituent groups having C—O—C linkages that the solubility in analkaline developer changes as a result of scission of the C—O—C linkagesunder the action of an acid.
 7. The resist composition of claim 6wherein the resin (A) is a polymer containing phenolic hydroxyl groupsin which hydrogen atoms of the phenolic hydroxyl groups are substitutedwith acid labile groups of one or more types in a proportion of morethan 0 mol % to 80 mol % on the average of the entire hydrogen atoms ofthe phenolic hydroxyl groups, the polymer having a weight averagemolecular weight of 3,000 to 100,000.
 8. The resist composition of claim6 wherein the resin (A) is a polymer comprising recurring units of thefollowing general formula (2a):

wherein R¹ is hydrogen or methyl, R² is a straight, branched or cyclicalkyl group of 1 to 8 carbon atoms, x is 0 or a positive integer, y is apositive integer, satisfying x+y≦5, R³ is an acid labile group, S and Tare positive integers, satisfying 0<T/(S+T)≦0.8, wherein the polymercontains units in which hydrogen atoms of phenolic hydroxyl groups arepartially substituted with acid labile groups of one or more types, aproportion of the acid labile group-bearing units is on the average frommore than 0 mol % to 80 mol % based on the entire polymer, and thepolymer has a weight average molecular weight of 3,000 to 100,000. 9.The resist composition of claim 6 wherein the resin (A) is a polymercomprising recurring units of the following general formula (2a′):

wherein R¹ is hydrogen or methyl, R² is a straight, branched or cyclicalkyl group of 1 to 8 carbon atoms, R³ is an acid labile group, R^(3a)is hydrogen or an acid labile group, at least some of R^(3a) being acidlabile groups, x is 0 or a positive integer, y is a positive integer,satisfying x+y≦5, M and N are positive integers, L is 0 or a positiveinteger, satisfying 0<N/(M+N+L)≦0.5 and 0<(N+L)/(M+N+L)≦0.8, wherein thepolymer contains on the average from more than 0 mol % to 50 mol % ofthose units derived from acrylate and methacrylate, and also contains onthe average from more than 0 mol % to 80 mol % of acid labilegroup-bearing units, based on the entire polymer, and the polymer has aweight average molecular weight of 3,000 to 100,000.
 10. The resistcomposition of claim 6 wherein the resin (A) is a polymer comprisingrecurring units of the following general formula (2a″):

wherein R¹ is hydrogen or methyl, R² is a straight, branched or cyclicalkyl group of 1 to 8 carbon atoms, R³ is an acid labile group, R^(3a)is hydrogen or an acid labile group, at least some of R^(3a) being acidlabile groups, x is 0 or a positive integer, y is a positive integer,satisfying x+y≦5, yy is 0 or a positive integer, satisfying x+yy≦4, Aand B are positive integers, C, D and E each are 0 or a positiveinteger, satisfying 0<(B+E)/(A+B+C+D+E)≦0.5 and0<(C+D+E)/(A+B+C+D+E)≦0.8, wherein the polymer contains on the averagefrom more than 0 mol % to 50 mol % of those units derived from indeneand/or substituted indene, and also contains on the average from morethan 0 mol % to 80 mol % of acid labile group-bearing units, based onthe entire polymer, and the polymer has a weight average molecularweight of 3,000 to 100,000.
 11. The resist composition of claim 6wherein the acid labile group is a tertiary alkyl group of 4 to 20carbon atoms or a group of the following general formula (5):

wherein R⁸ is a straight, branched or cyclic alkyl group of 1 to 8carbon atoms or an aryl group of 6 to 20 carbon atoms which may besubstituted, h is 0 or 1, i is 0, 1, 2 or 3, satisfying 2h+i=2 or
 3. 12.The resist composition of claim 3, further comprising (D) a basiccompound.
 13. The resist composition of claim 3, further comprising (E)an organic acid derivative.
 14. The resist composition of claim 3,further comprising (F) an organic solvent which is a propylene glycolalkyl ether acetate, an alkyl lactate or a mixture thereof.
 15. Aprocess for forming a pattern, comprising the steps of: (i) applying theresist composition of claim 3 onto a substrate to form a coating, (ii)heat treating the coating and exposing the coating to high energyradiation with a wavelength of up to 300 nm or electron beam through aphotomask, (iii) optionally heat treating the exposed coating, anddeveloping the coating with a developer.
 16. A process for forming apattern, comprising the steps of: (i) applying the resist composition ofclaim 3 onto an inorganic substrate such as a SiON film to form acoating, (ii) heat treating the coating and exposing the coating to highenergy radiation with a wavelength of up to 300 nm or electron beamthrough a photomask, (iii) optionally heat treating the exposed coating,and developing the coating with a developer.
 17. A process for forming apattern, comprising the steps of: (i) applying the resist composition ofclaim 3 onto a substrate to form a coating, (ii) heat treating thecoating and exposing the coating to high energy radiation with awavelength of up to 300 nm or electron beam through a photomask, (iii)optionally heat treating the exposed coating, and developing the coatingwith a developer to form a pattern profile, and (iv) heat treating forcausing the pattern profile to flow for thereby reducing its size.